It has come to my attention that many people don't quite understand gaining new policies in Civ 5. I've read quite a few people argue that gaining culture shouldn't become harder as you add more cities because well, you have more cities and population and should therefore have more culture. The thing is, you are getting more culture but changing a social policy for an entire civilization becomes more difficult the larger the empire is; hence the more difficult in gaining a new policy with a larger empire. Think about it. The US had an easier time switching to democracy in it's early stages but lets see how long it would take the US to switch to a different form of government or values now that it is much, much larger.