Because they have strong wings. If there are 30 hours, I can sleep well, swim for a long time, listen to music, and study. We have vacations in spring, in summer, and in winter. In spring the school year begins. Summer is too hot.
Winter is too cold and snowy.
Fall is a good season. We can eat a lot, read a book, and play sports. If fall is not a good season, we will have a fall vacation. Ten years ago I wanted to be a doctor. Now I want to be a doctor, too.