Nobody is denying you can slide in normal trainers, but why is it so hard to believe that professionals have personalised equipment? It's ridiculous to suggest otherwise, actually.
I don't get what's so hard to fathom.
cause it works in a different way.
first you need to become relevant for a company to make personalized gear for you.
and guess what, you need to use the retail stuff for this.
then, and only then you might get personalized stuff.
if you take tennis only.
there are appox 1500 pro tennis players.
do you know how many of them are not sponsored?
which means that they play with retail shoes, retail frames etc.
even if you take the gifted juniors, that might get special treatment.
first they learn to play in all usual retail gear.
only when they "shine", only then they might get access to some privileged service.
NOT the other way around.