At least in Google’s case it makes good business sense - as in, it already works for them and their target audience already has been using the OS with all that, and doesn’t care about it, ads and tracking; besides there aren’t too many phone OS options.
But in the case of Mozilla? Heck the target audience cares very much about these things and not liking shit like this was a reason they were in Firefox for. Now a lot have already dumped it for Safari, Brave etc. Then they keep doing such tricks.
Someone at Mozilla has to be especially dumb to have done this.
If there were a viable non-chromium alternative to Firefox I’d already have switched.
Edit: this is not completely true - I enabled Private Relay (Safari only) and installed uMatrix and uBlock Origin on Chromium, but that's about it.
I recently switched from Edge to Firefox (on both Desktop and phone) specifically because Edge was showing me irrelevant "news" articles (which I assume are just ads in disguise) [1].
I guess on phone I can move back to Safari (which I abandoned due to a bug where scroll position is frequently lost when navigating backwards), since it is apparently the only major browser that hasn't tried to show me ads.
Not sure what to do about desktop...