Heh! We have those ladybug invasions in winter too. They love our window frames. :P
So yeah, we probably don't strictly need to put up nesting places for insects, as there are plenty of dead trees and patches of uncut grass etc. all around - but on the other hand, it doesn't hurt, either. (At least I can lecture people about biological pest control when they ask! ;)) If nothing else, they're decorative. *g*