Let's get back to the original question.
Yes, the PPL is a pilot license and has nothing to do with maintenance, at first glance. But, from tradition it has been assumed that a pilot has basic knowledge of all relevant mechanics of his plane to repair it on even remote places of the world. By this, a privately operated even licensed light aircraft can have a certified maintenance manual on basis of so-called pilot-owner maintenance. For the certified part the manual has to state which maintenance can be done by the screwing hobby mechanics - i.e. 50h/100h/200h maintenance can usually be done by pilot-owners, annual has to be done by a part.145 organization, so at least once a year somebody does have an eye on it. There is a very large variety of things allowed to be done by this pilot-owner and yes, it is coupled to the license by the above mentioned reason.