I'm afraid it doesn't have much to do with chemistry.

@Mithoron This is what I was told by many chemistry teachers when I was a student. They also told be that lesser energy --> More stability. And every thing in nature wants to be more stable. Although I never quite got their 'nature' arguments, like XYZ chemical reacts in a particular way because of its nature etc etc.

It's very basic physis problem - in chemistry it's get as given. Enthalpy should decrease entropy increase.

@Mithoron That's exactly what my question is. Why should Enthalpy decrease and entropy increase?

chemistry.stackexchange.com/questions/19150/… - your q. is more basic than that?

If your question is as incredibly basic as I think, it stems from why forces exist you can read for example en.wikipedia.org/wiki/Force but it's primary propery of the universe - it's like asking why time exist or what is mass.