As the old saying goes
“If a person is not a liberal when he is twenty, he has no heart; if he is not a conservative when he is forty, he has no head."
It's easy to be idealistic when one is young and free of responsibility. When one is older and burdened with what life entails it's hard not to surrender the idealism for pragmatism.
This guy has done some research on peoples voting habits and found that people are likely to vote due to there personality and the reason people become more conservative as they age is that they gain more Conscientiousness. Which ties in with your statement. He has a lot of interesting stuff on youtube here's one you might find interesting.
https://www.youtube.com/watch?v=yo3gOoOSdhY