Like, all these projects are built by unpaid volunteers and have amazing documentation. We’re paying you a lot of money - what’s your excuse?

This is so true and it boggles my mind.

I understand the open source side of things. I write good documentation because every minute I spend on that saves me an hour in answering questions. It also helps any new employees get up to speed. And honestly, it helps me keep up to speed because I'm way too old to keep all this stuff in my brain long-term. I can't remember half the shit I did last year. Not in sufficient detail, anyway. I'm kicking myself now for not documenting all the steps I took configuring my personal Linux desktop, because I hopped distros and now I have to re-learn things I haven't done in years.

I don't understand the commercial side of things, because...aren't you paying your support people? Isn't that time costing you money?

Is the issue that the salary of the people with the technical knowledge to write good documentation is much higher than the support staff? Is it that paying customers by and large will not read documentation anyway? Is it because they are reserving the right to change everything radically without notice, and to hell with semantic version numbering?

Or is it that operational/ongoing expenses are easier to justify to beancounters than capital/one-time expenses in general? (Which seems totally backwards to me.)