We elderly cats do sleep more than younger ones but it's just old age, as some ignorant humans think. We may be in pain.
One estimate is that a third of all us cats suffer from arthritis.
We don’t show pain like dogs do. We don't complain. We don't whine or wimper. Most of us don't even limp. We don't show that we are hurt, like humans do. We just suffer in silence and do more sleeping. If humans were more observant they would notice that we hesitate before jumping up, and we may have difficulties on the stairs. Some of us need to use a chair to get to our favourite high places. We don't play games like we used to.
Humans get painkillers from a doctor, but only 7% of arthritic cats get any treatment at all. Yet there are special diets and painkillers that would give us a proper quality of life.
Are you listening, humans?