Yeah, I don’t think t-shirts are necessarily bigtime tailoring candidates, but pretty much all pants are!
I currently have a brand of OTR pants that fit me nicely, so I don’t have every single pair of pants I buy tailored. But the difference is noticeable when I do have a pair done. I like Levis 514 jeans, but they’re cut for wider hips than I posess. A little take-in and maybe a different hem length drastically changes the way I look in jeans. It adds a tidiness that makes them more versatile.