They don't have to provide bulk-mailing services to non-government entities. This is where someone says "Mail one of these advertisement packages to every person in this district", and it's not actually addressed to you. This would raise the cost of mailing spam to the same cost as mailing real letters.

Not filtering, no, but I would like them to set bulk mail prices high enough to actually reflect the cost of the externalities of sending (and trashing) that mail. Fewer companies would send so much junk if they had to pay for its true cost.