The whole concept of patents is to encourage people to come up with new ways of doing things. They get a limited-time monopoly on it.
Other people can either license it, steal it, or come up with an even newer, different, perhaps better way of doing things. Then they can patent it. And the cycle of innovation continues. Case in point: Apple has a “slide to unlock” patent. Google came up with a different method, which they patented. Google’s is different, and may be better. They were forced by Apple’s existing patent to innovate.
(Side note: My father holds/held a number of US and foreign patents on esoteric yet valuable patents in his field. I feel quite strongly about this.)
I have a big problem with patent trolls, however.