That's because Loro Piana T-shirts don't have the logo on them. They do, however, cost many hundreds of dollars [1] so if your eye is discerning enough to spot one you can be sure the person wearing it comes from serious money. It's similar for other high-end lines like Hermes. To spot them you have to be in the know. Indeed, the ability to spot these well-disguised high-end products is itself social signalling among the extreme high end of wealth. (The same phenomenon exists in other Veblen goods, like wine.)
Louis Vuitton, on the other hand, famously has its logo all over its products [2]. But even there you kind of have to know what you're looking for. It doesn't jump out at you the way a Nike logo does.
I think we're talking past / agreeing with each other? Anyway, there are such amazing clothes out there in all price ranges, and people can look so good in them that I feel if people are wearing logos they haven't "read the user's manual". Just aren't even trying.
I know my attitude puts some people off, and I really do understand why, but it's not out of class snobbery, it's that I find advertising so visually repulsive.
Louis Vuitton, on the other hand, famously has its logo all over its products [2]. But even there you kind of have to know what you're looking for. It doesn't jump out at you the way a Nike logo does.
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[1] https://us.loropiana.com/en/p/man/polo-and-t-shirts/soft-t-s...
[2] https://us.louisvuitton.com/eng-us/products/monogram-gradien...