Linux

I'd say it's because:

1. the people who ask for recommendations won't like (or understand) debian? (it's just "old packages this" and "outdated that" for most people)
2. the people who do use and appreciate debian don't read "I hate windows pls recommend me a distro" posts (or at least don't reply as often as the fanboys)

And, no, I don't use debian myself.

but when I finally switched over to Debian, everything just worked!

That's most probably because you learned how to use your system without breaking it in the meantime :)

In my experience, the Debian installer is just confusing. Once you're past that, the userbase is smaller than Ubuntu's. Their repos are different too, meaning software packaged for Ubuntu isn't guaranteed to work on Debian. Ubuntu itself is pretty terrible for its own reasons, so when asked for a desktop Linux distribution "close to Ubuntu" I'd put Mint first. (For general recommendation, I'd probably say Fedora now.)

Debian 13 is still relatively new, so the problems of it being out of date aren't showing yet. Debian 12 just before 13 released had tons of these issues, like glibc being too old for some binary programs, or the kernel not being new enough for some "gaming" features.

For reference, I am on Arch Linux. I feel I have a good understanding of how to manually install Linux. The Debian installer confused me in many ways, the main one being that "language and region" are closely tied, and selecting en_US "language" forces you to choose an American timezone later in the installer. In general it was a slow install process too. This is something other "user friendly" distros handle much better. A default live environment, a quick installation, and options being there, but having the defaults automatically correct (like timezone).

Like (almost) every other distro, Debian has its own benefits and downsides. These make it a good fit on desktop for slightly more experienced users, or users familiar with apt. This means it isn't in the list of distros I'd generally recommend to people when they're not familiar with Linux.

I use Debian for my desktop, and 100% think others should, too.

Might sound weird but I feel like it's cuz their website is boring. Debian doesn't do anything revolutionary, either. It's kind of boring to run.

I've tried every other major distro but always come back.

I haven't messed with Debian in a while but I remember the install being a hassle for all of my devices. But in my experience when I go to compile something I have to tediously update scores of libraries as dependency issues metastisize throughout the system. At some point I think to my self "who am I an Ubuntu developer or something?" and I go download some upstream distro like Ubuntu or PopOS.

I think those who know about Debian would already know if Debian's for them or not.

I'd generally recommend something a bit more beginner friendly to somebody asking for a distro recommendation.

From my experience as someone who uses Ultramarine Linux currently: The download page is fine, but not great as a new user. That alone kind of pushed me away, since I wasn't sure if I was downloading the right ISO. I can definitely tell the packages are outdated. I like GNOME desktop (which is what I downloaded), but I definitely know that other distros make customizations to GNOME that I had begun to take for granted (e.g. pre-installed taskbar via GNOME extensions). I could definitely use Debian but I find it just... a bit behind? Like it definitely works, but other distros are slightly more user friendly. Debian can be customized to match those other distros, especially with Flatpak, but any distro that isn't user friendly out of the box I don't want to recommend.

Debian always has been a stable distro. But earlier it lacked some good DE. And most beginners didn't know or thought it was daunting to install DE. That's why it got left out but now in past 4-5 years it has been pretty good.

Because it is barebones. New users need a distro to be configured for them to reasonable defaults.

I recommend Linux Mint Debian Edition to anybody who will listen

It's default installers aren't as newbie friendly IMO. And the defaults/theming are a bit bland out of the box.