Social and Promotions should basically just contain the "unimportant crap". If something is mis-categorized, you can drag it to the correct section and Gmail should learn from its mistake.
Also, as mentioned below, you can revert to the un-tabbed inbox by going to the Inbox section of the settings and disabling all tabs other than Primary, or by selecting one of the split inboxes (Unread first, Priority, etc).
Also, as mentioned below, you can revert to the un-tabbed inbox by going to the Inbox section of the settings and disabling all tabs other than Primary, or by selecting one of the split inboxes (Unread first, Priority, etc).
Disclaimer: I'm a Gmail engineer.