Not an expert but: married women covered their hair to make them less attractive to men. (Religious Jewish women now often wear wigs that look better than their natural hair, but that's OK. The Jewish God sometimes allows loopholes and workarounds.)

Not wearing mixed fibers was never a practical rule, but part of a common theme in Judaism of separating things, like separating milk and meat. Most importantly, the sacred is separated from the mundane, and the Sabbath is separated from work days.

There are quite a few rules in Leviticus that are impressively practical for an ancient people with a primitive understanding of biology: there are restrictions on a touching corpses or people with skin diseases, and frequent handwashing is mandated, including before eating, after urinating or defecating, and after visiting a graveyard.