I can't speak for all cats, but we have to be careful about our cats when the loft ladder is down. They were kittens whilst we were moving house earlier this year, during which time the loft ladder was down a lot, because we had to sort out all the stuff that was up there. The kittens went up in the loft every time they could, and on at least one occasion, we had to have all three boys and dh up there to try to get one of them out from his hiding place in the rafters.