Sassy,
Knee Socks Health Issue
The requirement of knee sock in powerlifting is for health reasons moreso than to protect the shins. The high knee socks keep blood from getting on the bar.
In powerlifting (any sports) an athlete who's bleeding (especially on equipment used in competition) is required to stop the bleeding or is removed from "the playing field".
If a lifter does bleed on the bar, the meet is paused until the bar is cleaned with a disinfectant. Thus, the rule requiring knee socks pretty much eliminates that health issue and having to stop and restart the meet.
Soccer Shin Guards
High knee socks provide a little buffer for the shins but not that much.
Some powerlifting organizations allow shin guard to be used at meets. Some powerlifters use Soccer Shin Guards in training.
Sweat pants work ok for me. However, shin guard appear to provide a bit more protection.
Kenny Croxdale