Why are E-books so short

I have to say lately i have been reading a lot of m/m e-books, and I am sad to say that they are so short that I am  reading them in under an hour. I am trying to figure out why they rush a good plot to may be anywhere from 50 to 100 pages. I mean a good story does not need to be rushed. I wish the authors and publishers make the e-book a little bit longer.