The last time I was on tour with A Forest of Stars (Victorian Black Metal Steampunk eat your heart out!) band t-shirts were a bit of a thing.
For a start, bands that were three days into the tour would use their merchandise shirts as spare shirts. Not to mention shirts being swapped between bands instead of being bought. I've also learned that it's a bit of a faux pas to wear your own merchandise, no matter how much it appeals.