No it's not bad to sleep on the floor.
Sleeping on the floor can actually be better for you and your health than sleeping on a mattress.
Sometimes I will lay on the floor and watch TV and when I fall asleep on the floor I find that I sleep much better and get more rest.
I wake up in the morning more refreshed for some reason.
I usually sleep on my mattress in my room but when I find that I can't sleep much I decide to sleep on the floor and when I do sleep on the floor instead of sleeping on my mattress I sleep much better.
In some countries most people sleep on the floor because they believe it's the best way to sleep and maybe they are right.
So if you want to sleep on the floor there's nothing wrong with doing so.