Most standups create their own unique material, or pay someone to write specifically for them, whereas many bands perform other peoples material (which is why ASCAP exists) as a matter of course.
If this meets with your approval consider how you'd feel if you went to a comedy club and saw someone doing Bill Cosby's "Noah, it's the Lord" routine versus how you'd feel if you saw someone doing it at a party.
I think that music is a much better model. We are magic stylists, for the most part. The classic tricks, like the classic songs, are presented as well as we can. The bad copy without feeling. The good copy with real feeling. The great create new phrasing, arrangements and presentations. The few immortals sing beautifully what has never been heard before.
That is why some people can create brilliant tricks but not perhaps perform them. Others take the work others create and make it sing. The few immortals will make their own creations rise to great heights.
But first, they all must study the craft, learn their classics, understand what has gone on before.
A primitive painter doesn't have less talent than a trained artist, he simply doesn't have the knowledge of what has gone before, and so continually reinvents the wheel. He might be great, he might be original and powerful, but he will never be a master of his art.
By the way, the modern standup comedy performer is much different than the great joke tellers that preceded them. Because of Lenny Bruce, standup became a form that expected the performer to be original in his material, and to draw from his own life-experiences.
In the days of television, theft of material becomes more perilous, but it still happens. Comedians sometimes look down on magicians because to them, it seems as if all the magicians go to a magic shop and buy a set of rings, a rubber chicken, and some other stuff and then put on a show. This has some justification, especially with the number of bad comic magicians who have done just that. Comedians have a hard time understanding that the linking rings can be performed by many different performers in many different ways.
For the magician, it is often a matter of showing the crowd something they have seen before like the linking rings, but in a new way, and of course making them like it one more time.
I'm going to sing you that old favorite...