What are the advantages of self-service car washer?

Self-service car washing machine has coexisted with manual car washing and automatic car washing for nearly a hundred years in developed automobile culture countries in Europe and America. No one can win them all, because each has its own advantages.

Many people think that the advantages of self-help car washing are low price and cheapness, but they are not. Otherwise, I haven't seen many Porsche, Bentley and BMW owners coming to wash it. Why? This is not cheap to explain.

In fact, the most important advantage is convenience, and convenience is the main feature of self-service car washing mode. what do you think?