Guy will know

But toilet paper exists

Yeah, but why do that when you can avoid mess all together

Because it means not making your socks dirty, and it's kind of awkward for your parents to have to clean those socks, whereas toilet paper can simply be flushed

If you're masturbating, I'm pretty sure you're old enough to do your own washing.

Or at least have enough dignity to wash your own cum sock

Yes but I find it easier to flush toilet paper than to do laundry
Look, I just never felt the need to use socks for that, is that really such a horrible thing?