If you want to get rid of the USPS all you have to do is make them use metric measures. Because Americans will sooner stop using the USPS than learn the metric system.
People’s expectations are conditioned by what they grew up with and most of the arguments boil down to “because that’s how we’ve always done it”. But that means progress is undesirable and also that what should or should not be kept depends on what you grew up with. Telegraph companies were mostly state-owned in Europe but private in America. Same thing with Telex and telephone. Telegraph and telex had their heyday and then declined. What is the point of keeping something for which demand is quickly diminishing? Where does it say that no one should be subjected to change and that we have a right to continue with what we had?
Gasoline in Spain used to be a monopoly and it had the exact same stable price anywhere and everywhere and people liked this predictability (never mind that it was extremely expensive everywhere alike). Many people could not fathom that something as necessary and essential as gasoline could fluctuate with the market and that people here might have to pay more or less than people over there. But there is no intrinsic reason, only what they were used to. Then the EU came, prices fluctuated with time and place… a few people grumbled but soon everybody got used to it.
I hate it when a product I buy is discontinued but I don’t think I have a right to it. So what if some people like to have mail delivered 7 days a week? Where is it written that the whole of society needs to pay so that those few can enjoy that convenience? Especially when experience shows other people are moving to more convenient ways of doing things.