I'd like to add my perspective here, and this is an area I have a professional interest in.
What tennis racket companies like Wilson and Head are doing is intentionally deceptive: they are cheating.
Irrespective of the merits of an average player using a pro-spec frame, it is not for the manufacturers to decide what product a customer they never meet or speak to directly should use.
In most developed economies there is regulation of consumer markets to some degree. This regulation offers consumers protection from being misled or from being treated unfairly by companies who, by virtue of the information they have or collusion with other parties might disadvantage consumers and reduce effective competition (thereby making everyone worse off).
Some people have claimed that consumers are stupid or foolish somehow if they take manufacturers' claims at face value. I disagree strongly.
Consumers (i.e. people) are primarily driven by unconscious mental processes. They typically use short cuts and generalisations to make decisions. The people here might be experts on the exact specifications of a pro player's racket, but they might know very little about the composition of a sun cream or a car engine.
If you buy a sun cream that claims to moisturise your skin, or protect to a given UV level, or be good for sport, you have no way of knowing whether this claim is true. You buy and try and find out, having taken the manufacturer's claims as credible. The chances are that you will buy a brand that reassures you because of your unconscious associations with it: but you won't carry out scientific tests on the product; instead you'll have faith that it is what it claims.
There is no reason that someone buying a tennis racket should need to become an expert. What's more, even if they decide to demo a racket before buying it, they have to filter down the list available or they would be testing 100 or more frames (never mind that each would be strung slightly differently!).
That such a consumer might use the choice of their favourite player as a place to start is hardly surprising. Not least because the manufacturers delight in telling us this information, thereby implicitly signalling its importance as a consideration factor (or heuristic that could be used in such a buying decision).
And finally, speaking as a psychologist (who advises regulators on consumer-related issues), there is good evidence from experiments that people who believe they are using a pros equipment perform better at the same task than those using the same piece of kit but who believe it's just a regular item.
So all those people who want to understand every aspect of their favourite pros kit and replicate it for themselves might well be enhancing their performance as a result! The irony is, that in buying kit that they believe is being used by their favourite pro, but is actually easier for their less developed game, the manufacturer could be argued to be giving them the best of both worlds!
However, I believe the duplicity is unnecessary and unethical and should be stamped down on. I hope Wilson lose and that all the manufacturers who play this game are forced to change their ways.