Why do very few of Botticelli's mythical paintings exist?

Before Botticelli's time paintings had religious subjects or were portraits. That is what people commissioned from artists. The interesting thing is NOT that there are FEW mythological paintings, but that there were some commissions for mythological subjects. And from then on those subjects grew more popular.

It was not like today: an artist paints what he likes and tries to sell it. In renaissance times you went to an artist and asked him to paint what you want.

Also, a radical monk named Savanarola burned 'earthly pleasures' including some of Botticelli's work. For more information on Savanarola's influence, I'd go to the link below.