I’d go basic debian . Install flatpak and flathub to get any packages that are too far out of date or might get so. Any derivative or ubuntu derivative just sees like unnecessary extra dependencies to me.
Debian gives i think a wider choice of desktop environment than any of the derivatives on install, but I think they’re all much of a muchness really. Most of the DEs have the “Click something, window opens” feature.
It could be a form of bundling, tacit veritcal integratation, magin squeeze , price discrimination, tie-ins etc.
Various tricks oligopolistic companies use to prevent competition from bidding prices down - trying to extract a bit of extra profit. The harm is that people are paying more than they might - or for extra features they cant opt out of than they would in a free or open market. Likely the harm is very diffuse and no one person is all that bothered to be paying 10% more or whatever, but it all adds up.
Anti-trust regulators are so weak they don’t really have to try though. TBF it’s very hard to prove this stuff in court even if there was a political will to improve competition to benefit consumers.