Here's your answer:
Because there is too much laziness in the music industry. The reason why it sucks is because artists have found shortcuts to make large batches of cash, and everything they do revolves around making money. Now I'm not speaking for all bands when I say this, but for the majority that do it just for the attention, fame, and money. And that's mostly coming from the Pop and Rap sections, and some Metal. (The bad Metal, for that matter.) There are hardly any musicians left that do it for the improvement of music, and not just to put large wads of cash in they're pockets. And as these bands grow, you get stupid teenagers who find bands that are "popular" so they listen to it just because everyone else does. And then you have the radio stations who broadcast the bands who cough up the most cash, and they fail to broadcast anything worth listening to.
Now, I'm not saying all bands of today suck, but I'm just saying the music industry will get its ups, and it will for certain have its downs. Hopefully it will be better by next year. I also think the problem is, is that most bands have run out of ideas and they become lazy.