Why politicians make many promises during elections but after election don't grant these. Why?

Imagine yourself in high school and the position of president was open. You decided to run for this position but you needed to tell people something in order to win.

Maybe you said - if you vote for me, I will make sure that there will be pizza in the cafeteria at lunch every day!

Go you!

When you win, the principal tells you that no, you are not able to fulfill your promise of having pizza for lunch every day. It seems there are dietary guidelines the school has to adhere to and this would break the rules.

Did you mean to deceive people? Probably not, but you wanted to win so you said what you thought people wanted to hear.

Simply put, Politicians lie to get elected and most continue after getting into office as we are seeing nowadays under the Obama Admin. Most continue to persue their agenda like Obama and don't care and after awhile they lie so much that they even begin to believe their own lies too unfortunately, and this is exactly why people don't put much trust in their Governments

Some are lazy and care more about money than people saying "wow he was amazing"