Sure, but their logo is still on their product even if they do sell clothing commercially. So why is it OK for Tommy to just buy their clothing and wear it in front of thousands of people without being sponsored, when Baghdatis still has to use a blank racket?
Players don't use blacked out rackets because they're not allowed to use a normal racket, they use blacked out rackets because they don't want to give whichever manufacturer free advertising.
They may also be using a blacked out racket whilst under sponsorship (mainly in training, though) whilst they're using an old frame not updated with the latest paintjob or testing a new model or more likely pro stock.
And there have been lots of players that aren't under sponsorship wearing a brand.