Why do people think being a materialist is bad? I don't get it.

I don't get why people are so against materialism. I understand it's not always the best thing in the world; buying things just because you can and buying things and accumulating massive debt makes sense. But being able to buy things with your hard earned cash shouldn't be frowned upon. That's the point of money in the first place. You earn some, you spend it on things you want and need and being able to afford things you want is a privilege that I don't think should be attacked. Sure you don't need some things and people shouldn't buy you happiness but since money and materialist things do exist shouldn't we be able to enjoy it. I don't get why people think it's bad to want certain things.