No i am pretty sure a naked bed is way better, lol so water/moisture can actually dry faster, instead of lingering on under/in a matt.
Like people who put on those leather or vinyl front bras on their cars and trucks to protect the paint from debris and stuff.... only to find out when they take the bra off, the bra has rubbed and scratched the paint raw and has done more damage than good.
My bud had a sweet white 92 camaro z28, he put on that black bra thing up front, had it on for a year and took it off to clean, and it had rubbed the paint down to the bare metal and looked like crap... he was so pissed, lol.
As for the bed matt and hard drop in bed liners... only good for short term use, throw them in when hauling wood and stuff for work, but don't leave in all the time...