My new friend Misha in New Zealand asked me a question last week. Actually, his mum had the question. She wants to know why cats sleep so much. Misha told her that it's because we can, but she wants a better answer.
Well Misha, I have done some extensive research on your question and the best answer I can find is: because we can. Other places I looked said things like this: On average, cats sleep about 16 hours a day, which equates to about two-thirds of their life. In fact, cats get more sleep than virtually any other animal, about twice as much as most mammals. Thus, sleeping is simply a normal behavior for cats. Just how much a particular cat will sleep, however, can depend upon many factors, including their age, their degree of hunger, their sense of security, the temperature and the weather.
Other answers said it's because cats are most active at dusk, and that we need to sleep a lot during the day to conserve energy so we can play Thundering Herd of Elephants at night.
I hope that helps your mum with her question, Misha!