I think that door to door delivery is outdated and should be stopped. For a company (or entity) to be hemorraghing money like the USPS has for the last few years, they need to do whatever they can do to stop the losses.
As far as the poor, they can walk a mile to a mailbox. The elderly can have whomever helps them out pick up their mail for them. If they are unable to go get their mail, then certainly they have people who help to care for them.
I also like Winchester's idea of cutting back delivery to a few days a week. Hell, I don't do anything with the mail anymore. Most everything I do, I do online. All my bills come to me online, I pay them all online. All I get in the mail is a bunch of junk mail and catalogs that never seem to stop, no matter how many times I ask them to stop sending them.
I also agree with AW - even though I get nothing but junk mail, I always am anticipatory about going to the mailbox and getting something cool - something unexpected. But it's always junk mail or those damn catalogs.