I tend to find that older (10+ years) t-shirts shrink a lot. Even if I don't wash them.
I literally have a t-shirt from 1997 that doesn't shrink in our machines. :D
It's weird, I never had that problem yet suddenly my old clothes started shrinking a couple years ago too.
Might have been our new hangers.
Same happens to me, but I don't think it's the T-shirts that are shrinking.