I’m a big fan of rock and metal music and often go to concerts. I’ll always buy a t-shirt of the main band I go to see, even if I don’t particularly vibe with the design, because I know it’s an additional way to support a band I like.
In my opinion that alone is worth it, but it is a fun piece of memorabilia. Although I don’t wear most of them in my day to day, especially the older ones.
I’ve got shirts from about 2008 onwards, which is the year I first went to see Sabaton and Disturbed.