They keep stuff out of your boots
Thorns out of your legs
Ticks out
Powdered snow out
Dust and pebbles out
Crampon spikes out.
You can wear lighter boot/shoe
When walking through low brush sage, heather, desert, from the knees down you are protected without the weight.
When crossing Alder patches in AK, no sticks penetrate.
They are just a practical inexpensive bit of gear that were common up through WWll but fell from broad use in the US outside of hikers and mountaineers.
If you ever use spikes or crampons, they are essential.
Once you start wearing them you will always wear them. I liiken it to my dogs. Without any protection they will still bust through the bush but put a vest and googles and they become a bulldozer when they realize they aren't getting hurt.
