I remember that I did sometimes sit on the floor when young, and I also lay down on it, but not as much as sitting. I eventually out grew it. I seem to remember that this happened in my early twenties. Now that I am in my 50s I won't because of really bad knees. I did have to sometimes when I had dogs, so that I could take care of some of their needs. Sometimes they needed their nails clipped, or stuff picked up on walks removed from between their toes. Once, I was walking our border lab cross and noticed he was walking like he had something between his paws, as he had had on many other occasions, but for once, I couldn't tell by his gait, which paw it was. For the heck of it, I checked all four paws. Yes! He had stuff in all 4 paws!
He was always good about letting me fix it, because he knew I was fixing it. Unfortunately, the last few times I was on the floor with him were to feed him bits of food off my fingers several times a day for his last few days of life, and then the last time I sat on the floor with him was at the vets, when we had to have him put to sleep. He had inoperable terminal cancer.
Due to health problems of my own, sitting or lying on the floor is too hard for me to do, and it is also no longer possible for me to have a pet, but I sometimes pet the neighbor dogs and cats.