I think #3 is close, but it's not just that some users concentrate a disproportionate amount of wealth. It's also the quirk of human society that great hoarding

I think #3 is close, but it's not just that some users concentrate a disproportionate amount of wealth. It's also the quirk of human society that great hoarding of wealth winds up distorting it such that economic worth becomes directly tied to human worth. This is undesirable generally, and taxes are the main mechanism for the government to regulate this tendency.