Why car rentals dont have Hondas?

Some of them do. I know for a fact that Enterprise rents Honda Civics and Accords, because I work for Enterprise and we have them in our fleet.

But one of the major factors in the types of cars available for rent is how much they cost. A rental fleet will usually be comprised of less expensive cars for the majority (usually GM, Ford, and Chrysler, as well as Hyundai and Kia). There are always some other types included in response to market demand. Some customers want a specific type of car. Some want only a Japanese car. So cars like Hondas will be available, but in significantly smaller numbers.