Why businesses fail?

Busniess fail to due lack of long run strategic management.When ideas are not translated into action.Other constraints for business can be lack of organization external environment analysis.An external issue can create direct effect on business.Lack of Product/Market classification might be another reason. 

For me, I would have said that businesses could fail for sake of two reasons- and may be more.

First, because of incomplete business plan. Second, because of incomplete business plan implementation.