These are a few of the ways we use old socks in our house.
If you use thermos flasks, like we do a lot for picnics and DH takes one to work every day, we slip ours into a sock, with a slit for the flask's handle. Protects it for years.
DH uses them in his shoe polishing kit. Whenever I get some lone ones, i just swap them out with the old used ones.
When my 4 sons were small, I always kept a few clean socks in the first aid-medical kit... often had skinned knees and elbows etc. Just cut off the sock toes, and they're a quick bandage for keeping bandaids and dressings in place on knees and elbows and shins.
We used to put a bar of soap in the toe of a sock, put a knot in it, and then tie the other end around an outside tap for the kids to have a hand and foot clean before coming indoors. No more soap left to lie in a slimy puddle. DH still uses one in the sink in his shed.
If the tops haven't lost their stretch, chop off the top few inches, and use like big rubber bands.. I found them safer than rubber bands for kids...around bunches of coloured pencils, holding lids on shoe boxes, etc.
But whatever you can't use, yes, just toss.