When someone is trying to break into a house, they might have to do it fast, so that they don't get noticed. If they need to pick two locks instead of one, it's costing them twice the time, so by locking the handle in addition to the deadbolt, you're increasing your security by making your door a bit more of a pain for someone to break into.
Who picks a lock to break in? Common thieves have no need to pick locks.. totally dumb for a couple reasons.
Contrary to popular nerd belief... door locks in the US are not that easy to pick. Many have anti pick features like reverse sidebars that while not impenetrable increase time or skill required. While the lockpickinglawyer has videos, note that he is extremely skilled with tons of practice, it still can take more time than breaking, and those aren’t field conditions.
Just break the door in... stealing might as well use forcible entry.
Where picking is useful is covert spying, and if that is your threat model the addition of the second or third lock doesn’t really mean much.
I don't know about these videos but when I called my neighborhood locksmith to deal with a lock I'd misplaced the key to, it took about 20s to pick... It would seem to make sense to me if you were trying not to call attention