That is the whole point of the patent system! That it gives the inventor exclusive rights to an idea for a fixed period of time.
Invention, not idea. May sound subtle but it's an important point. The anti-patent people think that you just have an idea in the shower and you can get a patent on it and that other people have the same idea and they lose out.
The reality is, it takes a lot to create a patentable invention, it's not protecting the idea, but a specific implementaion.... and if my experience is representative, original inventions are very rare.
One of my patents is about to run out, and despite the industry needing to solve this very problem for the past 20 years, and several other methods of solving it that I can think of (that are pretty obvious) ... people don't even try.
The patent (which nobody is aware of) doesn't prevent them from solving it in any number of ways.
But what the industry does is simply ignore the problem.
The patent was ahead of its time, obviously, but I am surprised that nobody has taken a crack at the problem at all in teh time period.
Hell, a patent violating implementation from somebody who came up with the same solution would have been great (not because the patent would be enforced against them, it wouldn't) ... but because it would show someone actually was thinking about the problem!
Nobody has even had the same idea in the past 20 years, despite a billion dollar industry which would benefit greatly from it....and if someone did have the idea, their implementation would likely be vastly different due to the advances in technology over the past 20 years, and thus not violating the patent.
The reason: people simply aren't that inventive.
Patents are protecting hard work, and something that is actually quite rare.