It could be that Gmail is optimizing for the lazy of us. That's my view on the Updates tab as well: I have unsubscribed from a bunch of this stuff, but I keep getting more of it, sometimes from new sources, sometimes from existing sources but new accounts, and other times from existing sources who have added new kinds of notifications my previous opt-out doesn't respect. At some point I gave up fiddling with it and just got used to the x# sequence (default Gmail keybindings for select-and-delete). Gmail putting it into its own tab is a net improvement in user experience for me, because now I can xjxjxjxjx# all at once. I might even give a brief glance at the subject lines, so they aren't necessarily useless. But I don't need to read them as emails, and I don't need them interspersed with my real email. Conceptually they aren't really emails, but an email serialization of a status update, like what you find under the little red number icon in Facebook. So I like them being shown as such, in a separate space.

It's all filters I could have set up myself, but the default filtering pretty closely aligns with my preferences, so for me at least it's working. And so far, Google has actually never moved out of my Inbox any email where I've opted in to receive the email. The only things getting filtered are things I never asked for.