Despite being completely hopeless at sewing, I do mend things, rather than throw them away. Today's society is so wasteful, why add to the landfill? And it's quite therapeutic - sitting quietly and sewing whilst doing something that will add some extra life to a belonging.
Ooh, no, I do not -even my mother, in her day, taught me to throw socks out many years ago instead of mending/darning them!
I do not like sewing, in fact I intensely dislike sewing -will cook all day, but not sew, so no, if I need an alteration/mending on my clothes, they go to the local seamstress and I am happy to pay for this service.
It depends. I throw socks away or underwear, but if there is a small hole in my favorite shirt, I will mend it. I also do small alterations like shortening trousers. I like sewing, but sometimes it's a waste of time. With socks it's totally worthless. They will get ruined again the next time I wear them.