For one, there are more people on Ubuntu. I believe, a large part of the reason for that, is the cadence. I don't exactly like Ubuntu and I decided to depart for Debian last year, I had had just about enough of Ubuntu quirks and antics. But I held fast for so long because of the cadence. You can set your corporate schedule on month == April && (year % 4) == 0 and be done with it, for the LTS releases. With Debian you have to be at least a little tuned in to current events. I don't like that, I have other things going on.
Ubuntu also has a cadence to the non LTS. So if you want to study ahead what could break, test your stuff currently deployed on LTS, on the latest regular stable.
This is my que to off on a tangent and remark that easy cloud and Kubernetes (oh dear don't get me started but it's also useful, so what can I say) has made whatever OS runs on the servers less important. But I still care for some things.
And I don't want to run testing. I like to keep just one step behind. Of course, not everyone can be like that or there wouldn't be any experimentation and progress, but there are plenty of other people filling that niche.
To let you know - you are not alone with such considerations and I completely share the point of massive scale makes sense and cadence makes sense for planning
They are probably referring to the Ubuntu Pro (previously Advantage I believe) notices that appear when you login via SSH or do apt updates. They can be disabled/hidden anyway, but they are still conceptually invasive.
