Why is it that the older you get, the less you trust?

Unfortunitly, I have found that to be true. The older I am getting, the less I trust my fellow man, the less I trust a stranger on the street, the less I trust my government, at all levels. Is it becouse time after time the corruption, the bad, has been proven true. Or is it becouse I didn't pay as much attention to these things when younger?

With age you learn about people, and are aware of much BS.

The older you get the more likely you are to have been hurt by people's selfishness and lies. 

Fool me once shame on you... Fool me twice, shame on me, applies here. 

As we get older we see through lies and stories faster. 

As for why people are so untrustworthy... People are selfish and that leads to inconsiderate behaviour choices.