QUESTION

In your opinion:

Which is the reason a lot of TV shows have crappy endings?
(ex. "LOST" , "Dexter" , "The Sopranos" , "How I Met your Mother" and so on)

P.S. 1:  You can add or disagree with some of my choices of course.
P.S. 2: I didn't include "The Mentalist" because I don't know, we have a whole season ahead; things can happen.