>There is no such thing as work that's absolutely crucial and not customer facing, so it makes perfect sense to disincentivize work that's shaped as you describe

I took a week to refactor some nasty crap a few months ago. No customer noticed it.

I was rather happy to lower the estimated time for a bunch of other tasks from weeks to days/hours after doing it.

Now you can argue that was not "absolutely crucial", but then we'll just disagree on what that means.