Your fish will survive without floating plants, but that doesn't mean they wouldn't be happier.
All of my gouramis/bettas hang out under the floating plants (riccia, specifically) and use it to support their bubble nests. It's also a 'comfort zone' for these guys.
One of my pearl gouramis always hid at the bottom in a decoration. Once my planted tank provided more growth at the surface, this guy never went back into hiding!
There's no doubt labyrinth fish feel more secure with floating plants.