My assumption is that it's less of a monetary loss for them to serve the ads unbundled compared to putting the engineering resources behind bundling them. They, obviously, have the exact numbers readily available, and I assume the "money lost" lines will cross eventually.

Regardless, there is a loss, and they'll respond to it when it becomes significant enough.

edit: uBlock Origin has over 10,000,000 users, according to the chrome web store. I can only imagine something will change soon, or there's some serious technical debt holding things back.