Honestly, end of the day, the deck doesnt make the magician.
And if you are great with a deck of Bicycles, you will be probably even greater with a 'Custom Deck' (Possibly) but it really doesnt effect it that much.
In a way you're right, but I'd think of it as more of a style thing. Of course, most important is that the deck will handle well enough when you're cutting or tossing or spreading, or doing whatever you need to do.
But assuming I have two decks that fit that bill, I will go for the one that has the style & look I like most. Having a cool deck will reflect on me, first impressions, when dealing with other people. Plus if nobody else cares, I'd admire them in my own hand or wherever I let them rest.
If you don't care how you look or how they look, then I guess you're better off fawning over other things. But personally I will always look for the best-looking best-handling deck I can find.