Companies don't want to pay you more just because there is a perceived value. They will only pay you once you threaten and you are good for it (supply demand) or you change jobs (supply demand again).

I have thought about this hard. Both as an employee back in the day and now for 6+ years as a business owner. As an employee, I thought the same as you but then stopped expecting from current employers. When I was ready to jump, I jumped. Period. No ifs. No negotiations with current company. As a business owner though, I definitely understand why I am not just going to give someone a 30% raise. Now, if you are a small company and there is no a whole lot of management red tape (like my company), I encourage anyone to ask for a 30% raise and be ready to be able to justify it. If you are worth it (capitalism), I would do it. But if you never ask, I absolutely won't give you a 30% raise. Remember, you are not the only one in the company.