I think it's just brand, ubuntu was what I knew from using it as a personal desktop and then it's the default/most obvious option for a lot of providers, I think even 10+ years ago AWS EC2 defaulted to it above Debian, digital ocean too I think?
I don't remember why exactly but it was definitely just 'linux VPS = Ubuntu' for a long time. I think they got reputation as being the 'just works' option because they were happier to include some non-free graphics drivers etc where Debian was the more pure option but most end users didn't care
But since they added snap and I started running into issues with trying to install Docker etc a few years ago I default to Debian now and most of the time I don't even know which it is.
Back in 2005-2008 or so, I think Ubuntu was a genuine breakthrough as a polished desktop version of Linux that set a standard that various other distros, eventually, caught up to. I think Cinnamon and other distros eventually caught up on polish.
They also had credible commitments to long term support that brought people on board. I think that was enough to get them on the map, but personally as a desktop user, I haven't used it in a while, mostly sticking to Debian and Arch.
Yeah this was the same for me. When I first made the switch to Linux for my dev machine Ubuntu was the distro I was by far the most familiar with so that was just the default choice. Later on after learning more and seeing how Ubuntu progressed I regretted not going straight to Debian.
I think you are right about the branding / reputation. Personally I heard negative things about Canonical and I heard that they just basically follow Debian, so why not use the original? It's been a great experience so far. Perhaps because Debian moved to include proprietary drivers out of the box now it is extremely easy to set up.
The brand I associate with Ubuntu over Debian is increased RAM usage and extremely low performance of the UI.
For us slow kids in the back, can you link to a .ISO-file of your favorite Debian?
Ubuntu found me (finally, with the tutorialhelp of a localLLM) in 2026, and I don't trust most of the opt-outs.
Stable Debian is using Linux 6.12, if your laptop has modern hardware what do you do? Can't use wifi?
And don't get me started with Debian testing. I want a LTS distro not a testing one.