You should respond and ask for honesty/clarity so you can avoid making the same mistake in the future. Maybe they will tell you. Could be anything from you don't sync with them creatively to you don't bathe enough. You don't know til you ask. If you really are a good musician and a team player, it shouldn't be hard to find another gig.

As far as the social aspect goes, that sucks but being in a band is a business. Friendships are only as good as the strength of the business. I've always had a robust social life outside of music. Not all my eggs in one basket as they say.