The reason for their dismal reputation is they were traveling entertainment. There were few towns large enough to support a permanent entertainment class, or the same acts on a repeated basis. They had to move to maintain novelty.
When things disappeared through theft, it was easier to blame the strangers who had just been in town than to blame local talent, and perhaps rightly so. payment for entertainment service was lowly, again because of the reputation of such itinerant movement, and in some areas one still had to pay for room and board above what one could earn. Thievery and prostitution were one way the artistes could make ends meet. The Illusionists and Magicians who did card tricks also get their starts as gamblers (dishonest) and pickpockets. So things DID disappear when such shows came to town.
Another reason for disapproval of such low-lifes is that travelers were a means of disease spreading among villages. Towns were insular and had little contact except for travelers. Any disease would likely appear a few days after the appearance of a band of such travelers/entertainers, especially sexually transmitted diseases.
Is it any wonder that people tended to look down their noses at such "low lifes?"
Excellent post, Swordy. 188% concurrence.
So good, in fact, that I set it to music.