What I value most

I can not understand why people do not keep their promise.
If I make a promise, I will try my best to fulfill them apart from some special cases. But to my surprise, I found most of the people did not keep their promises. They made promises, after a while, it was so easy for them to change their mind and just regard their promises as nothing and act as if nothing had happed, nothing they had promise to others.
Someone told me that you should not be sensitive with others' words . Sometimes people promise you something out of politeness or they say so just because of the need of social communication. For example, once a person told me he would buy a lot of happy nuts to me, at that time I believed him. But as many months went by, I did not even see the shadow of the happy nuts. Again, I asked a person a question, he told me he would answer me next time we met. I believed him again. But the same result came. He did not mention it at all. My heart hurt again. Firstly, he made the promise because of politeness. While in the second case, he ate his words and he made the promise again just because of the need of social communication. But I really can not accept such reasons. If we can not keep our promise, just do not make it.
As far as I am concerned, people do not keep their promise because they do not put the promises into their hearts (except the case that they really forget their promises). In other words, they do not care about you, so they do not care about what they promise to you. I know it is sad for us to accept it because that means people do not treat you as an important person.
In fact, breaking one’s promise is a version of lie. I admit I like to tell lies. For example, I tell someone my birthday is on the same day as his so that he can give me a present. Or I tell my friends to go out to look at the beautiful moon while in fact there is nothing in the sky. But I do not think that such white lies are wrong. They are just the same as we tell on April Fools’ Day. But another kind of lie is something that really hurt my heart. They tend to cover the truth, they seem to make beautiful promises to you while their do not keep.
I am really moved if someone tells me: I will keep my promise. I will put them into heart. Because it is what I really value most.
I hope if you can not keep your promise, do not make promise. People will be with the hope and wait for you to fulfill it. If you break your promise, it will let them down.