Why are most laundry products detergents instead of soaps?

They are the same thing, just with differing names.

Soaps are detergents and detergents are soaps. The names have become associated with their different uses. Soaps are now primarily used to refer to soaps/detergents used on the body, while detergents have comes to mean soaps/detergents used for things other than cleansing the body, such as dish detergents.