This is why I make my husband shop for his 14yo son. He 'collects' expensive sports shoes/sneakers (he seriously has, like, 20 pairs!) but otherwise has no hobbies, doesn't like to read, is too old for toys or collections, etc. I think last year DH bought him tickets to a university bball game & basketball shoes. He will likely do the same thing this year.
My 7yo is already hard to buy for at 7! She wants that ridiculous Hatchnimal, which I won't buy for her since I know she will play with it for 20 minutes and be bored, but otherwise really doesn't have any other toys or collections. She likes the idea of toys but doesn't actually play with toys regularly.