[Dalewyn]

A closed line of credit (eg: closed credit card, paid off loan) will fall off your credit report after about 7 years, lowering your score.

Having many inquiries from asking for new credit cards frequently implies you're trying to take on a lot of debt, which is a higher risk factor and thus lowers your score.

Buying with cash means you didn't take on debt, so that obviously doesn't factor into your credit score.

Parent is right, people (such as yourself) chronically don't understand how finances work.