The two menus essentially split the types of content you’re being linked to.
The hamburger menu has site-related links… navigation to various sections, admin links, etc…
The user menu is personal stuff… your notifications, your messages, your bookmarks, etc.
I think it’s completely fine that the hamburger menu isn’t frequently used, and that reinforces the separation. If we combined the two menus you’d end up more frequently seeing a lot of stuff that you don’t need to see frequently.