Why were shepherds detestable to Egyptians?

“When Pharaoh calls you and says, ‘What is your occupation?’ you shall say, ‘Your servants have been keepers of livestock from our youth even until now, both we and our fathers,’ that you may live in the land of Goshen; for every shepherd is loathsome to the Egyptians.” (Genesis 46:33-34 NAU) Why was every shepherd loathsome (an abomination, disgusting, abhorrent, detestable) to the Egyptians?

Here are some suggestions, from here.

 G. J. Wenham says, Shepherds are detestable to the Egyptians probably reflects a common distrust of nomadic peoples by urban dwellers (cf. attitudes to gypsies and ‘travellers’ in modern society). (The New Bible Commentary)

The IVP Bible Background Commentary says, It is unlikely that native Egyptian herdsmen would be detested by other Egyptians. Joseph’s advice to his father is both a warning about Egyptian attitudes toward strangers and a piece of diplomacy in that they would claim independent status (they had their own herds to support them) and show they were not an ambitious group who wished to rise above their occupation as shepherds.

Derek Kidner likes the explanation of J. Vergote:

A more likely explanation is that of J. Vergote, that this is only the perennial antipathy of the town-dweller for the nomad or the gipsy [gypsy]. Joseph saw the importance of emphasizing this, to ensure that Pharaoh’s goodwill would be to the family’s real benefit, not to their detriment by drawing them into an alien way of life at the capital. (Tyndale Old Testament Commentaries)

Howard Vos says, The reason for Joseph’s concern was that Egyptians considered shepherds an abomination. Settlement in Goshen would separate them from the Egyptian cattlemen of the Nile Valley and thus reduce friction with Egyptians and preserve their distinctiveness as a people. (Genesis in Everyman’s Bible Commentary)

John T. Willis points out that the term livestock (or cattle; Hebrew, miqneh) is “a comprehensive term including cattle, sheep, goats, and the like” (Genesis in The Living Word Commentary on the Old Testament).

We may add the opinions of

Clarke
1. Shepherds and feeders of cattle were usually a sort of lawless, free-booting bandits, frequently making inroads on villages, etc., carrying off cattle, and whatever spoils they could find. This might probably have been the case formerly, for it is well known it has often been the case since. On this account such persons must have been universally detested.
2. They must have abhorred shepherds if Manetho's account of the hycsos or king-shepherds can be credited. Hordes of marauders under this name, from Arabia, Syria, and Ethiopia, (whose chief occupation, like the Bedouin Arabs of the present day, was to keep flocks), made a powerful irruption into Egypt, which they subdued and ruled with great tyranny for 259 years. Now, though they had been expelled from that land some considerable time before this, yet their name, and all persons of a similar occupation, were execrated by the Egyptians, on account of the depredations and long-continued ravages they had committed in the country.
3. The last and probably the best reason why the Egyptians abhorred such shepherds as the Israelites were, was, they sacrificed those very animals, the ox particularly, and the Sheep, which the Egyptians held sacred. Hence the Roman historian Tacitus, speaking of the Jews, says: "They sacrifice the ram in order to insult Jupiter Ammon, and they sacrifice the ox, which the Egyptians worship under the name of Apis." Though some contend that this idolatry was not as yet established in Egypt, and that the king-shepherds were either after the time of Joseph, or that Manetho by them intends the Israelites themselves; yet, as the arguments by which these conjectures are supported are not sufficient to overthrow those which are brought for the support of the contrary opinions, and as there was evidently an established religion and priesthood in Egypt before Joseph's time, (for we find the priests had a certain portion of the land of Egypt which was held so sacred that Joseph did not attempt to buy it in the time of the famine, when he bought all the land which belonged to the people, Gen 47:20-22), and as that established priesthood was in all likelihood idolatrous, and as the worship of Apis under the form of an ox was one of the most ancient forms of worship in Egypt, we may rest tolerably certain that it was chiefly on this account that the shepherds, or those who fed on and sacrificed these objects of their worship, were an abomination to the Egyptians. ...
Gill

not because shepherds ate of the milk and flesh of the creatures they fed, which the Egyptians abstained from; for the Egyptians in those times did eat the flesh of slain beasts, see Genesis 43:16; nor because they fed, and slew, and ate those creatures, which the Egyptians worshipped as gods, as Jarchi; for it does not appear that the Egyptians were so early worshippers of such creatures; nor is this phrase, "every shepherd", to be understood of any other than foreign shepherds; for one of the three sorts of the people of Egypt, as distinct from, and under the king, priests, and soldiers, according to Diodorus Siculus, were shepherds, and were not despised on that account; for, as the same writer says, all the Egyptians were reckoned equally noble and honourable; and such it is plain there were in Egypt, in the times of Joseph, see Genesis 47:6; and goat herds were had in esteem and honour by those about Mendes, though swine herds were not: wherefore this must be understood of foreign shepherds, the Egyptians having been greatly distressed by such, who either came out of Ethiopia, and lived by plunder and robbery, or out of Phoenicia or Arabia; for, according to Manetho, it was said that they were Arabians or Phoenicians who entered into Egypt, burnt their cities, etc. and set up kings of their own, called their Hycsi, or pastor kings: and therefore Joseph might the rather fear his brethren and father's family would be the more contemptible in that they came from Canaan, which was near to Arabia and Phoenicia; but Dr. Lightfoot is of opinion, that the Egyptians, being plagued for Abraham's and Sarah's sake, made a law, that for the future none should converse with Hebrews, nor with foreign shepherds, so familiarly as to eat or drink with them.