This thing crashed in on itself, and there is a reason for it.
Releasing t-shirts with some weird, artsy stuff on it, and slapping a game on the sleeve. The shirt you are wearing says something about you. If you are wearing a shirt with Mario on it, that means you are a Mario fan, a game addict or a nerd. Wearing a simple blue shirt means you don't really want to stick out of the crowd...etc. Very few people knew about the games at the time, so buying and wearing those shirts meant one of two things. Either you are a nonconformist who wants to stick out of the crowd by wearing some obscure artsy shirt noone knows about, or you don't care what you are wearing just liked the design.
I don't think many people bought the shirts for the game. I think most of them though about the CD, like L.B. Jeffries said, some advertising junk, the game that came with the shirt and not the cool game that the shirt is about.
But if the game was marketed first, then the shirt released, it would've been simple merchandise, fan stuff, and there is nothing experimental about that. It's a Catch-22 right there...
Innovation became a bland concept and games used and abused it to the point where it means nothing anymore. People are tired of all the "innovation" around, every single piece of good is advertised as innovative, be it a game, software, t-shirt or anything else. People are tired of buying "innovative" stuff and getting the same crap they are used to. This is why they don't trust experimental things or really innovative stuff anymore.
I feel really sorry for the indie scene...