It's a natural progression for up and coming bands to evolve into something else. Usually it's something softer and/or something that the early adopters don't approve of.
Maybe they're chasing the dollar - I have no problem with that. Go make your millions, given the chance I would too. As a consumer, I just might not spend my money on it.
Maybe they get older and get sick of playing the same sh!t they played when they were younger. Bands are damned if they do, damned if they don't. If they never change they're just churning out the same old sh!t. If they do change, it's a bunch of crap that doesn't live up to the early stuff.
A great example for me is the Goo Goo Dolls. Unless I'm wrong, Buffalo origins. First I heard was Flattop from A boy Named Goo. Thought it was a great alt/pop song and really liked the album. Dug deeper and found their earlier albums sounded like the Ramones, which although I liked, sounded unoriginal. After that they went super-pop which I couldn't stand. I'm fine with liking their middle ground without condemning what surrounded it.
My overall point? Like what you like for whatever reason you like it, but expect bands to change.