They're the only type of "wearable" computers that make sense: i.e. computers you can easily carry in your pocket.

Occasional fantasies of computers built into actual clothes are the domain of people who don't understand clothes very well.

Exactly. There is nothing that would stop us from making smartphones water resistant and shock resistant and sowing them into clothes. It’s not that we don’t do it because it’s impossible, we don’t do it because it’s a stupid idea.

Ah, but think of the sponsor & advertising angle. Rent out the space on your t-shirt.

Eventually every surface will turn in to an ad. And animated ads after that. The animated t-shirt can't be all that far into our future.