Every day I clear out my mailbox and 95% of the contents goes directly into the recycle bin. I have tried all the DMA removal forms, various generalized opt outs, etc., but the junk mail keeps coming.
Recently with paperkarma (an IOS app) I've been able to reduce it somewhat, so now junk mail is about 75% of the contents of my mailbox on a bad day.
There is certainly no reason for daily deliveries. I'd be happy with once or twice each week. This would save massively on fuel and labor costs and would not degrade the service significantly since the trucks could still operate between cities every day if necessary.
The USPS and the paper direct mail industry should both have gone away long ago. Alas, it's illegal for any companies to offer standard letter delivery services, so the USPS is also a monopolist, with all the expected bloat and inefficiency.