Because human ignorance --- humans can not explain the existence;
Because humans expected --- there is a gap exists and expectations;
All of the problems are in human knowledge and transform the world produced.
This is no problem in the world, until there are people. People a purpose, objective objects created expectations, and the status quo with the objective target object of a gap, so have the problems. To compensate for this gap is the process of solving the problem.
Apply what they learn is the ultimate solution to the problem of theory.