I do some mending, but not a lot. Socks, those tend to go thin for me rather than get holes, and there's no saving a worn-thin sock! I toss them into a rag bin - I use them for things like dusting, or for wiping off muddy dog paws. I'm also saving the thicker ones for moving - someone gave me a great idea of using old socks to pack things like glasses in - just slip a (clean) sock over each glass! Genius!
I don't sew buttons for DH - I taught him how to do that himself when we were teenagers (before we even started dating) and he's still pretty proud of that skill, so he sews all his own buttons. Anything that requires a sewing machine, however, is up to me.
He telecommutes, so around the house in the summer he wears these thin cotton "lounge" pants, and our dogs and cat are always on his lap and their claws go through his pants on a regular basis. He doesn't care how they look, so I go ahead and darn the rips, usually with a bit of muslin fused on the back to reinforce it. Some of his favorite pants are mostly darning and muslin patches by this point, lol, but he says they're still comfortable so...whatever! If he's happy, I'm happy.
I have gotten really good at taking out and putting back in those long leg seams!
I do fix and adjust cuffs and hems, but few alterations beyond that. I also cheat a lot - a fallen-out bottom hem on my (cheap) work pants is almost certainly going to get fixed with fusible tape rather than a proper blind hem stitching. I'm not so good with the blind hem stitch, but I'm great with fusible tape!
I've never sewed a garment from scratch but I'd like to, some day.