I'm not quite sure I agree with the tennis analogy, it's more a question of concerts vs. busking:

If you have paid for tickets to a public performance, your expectation is to see the best possible show. This is certainly what the tennis players provide, but their lack of interest in the audience (Ilie Nastase excepted!) is due to the competitive nature of the activity. If you go to a concert, you expect the performers to be well turned out and well practiced, entertaining to the best of their ability.

Busking is done to a transient audience - if you don't like it, you move on, you are in no position to demand your money back or to express disappointment with what you witnessed. If the buskers are poorly turned out and less well-practised, that is to be expected.

It is also the case that many impromptu street shows are more entertaining than formal concerts.

My issue with scratch morris teams is if they cross the boundary and participate in formal events where public expectation is particularly high. I must say, I have danced with many scratch teams at festivals and morris events, we have often outshone the "official" teams and have put on a highly entertaining show, but on none of those occasions did we try to gatecrash formal shows uninvited.

IF the Motley and Whitby scratch teams are guilty as charged, then while it is true that this is an issue the festival organisers must deal with, it is also the case that they are opening the whole of the morris to unjust criticism and/or ridicule (i.e. for the standard of what they do, not the nature).