2.
> help users stuck on old versions of the OS use a normal browser
Funny, iOS tends to be upgraded further back (ie support older devices), and faster [2], than (say) Android [3], because Apple is aggressive about updating users.
[1] https://gs.statcounter.com/browser-market-share
Which really sucks on iPads, because not real free adblockers, faulty SVG rending in safari for a project I ran two years ago, and less support for browser features (PWA features mostly, so classical web often kinda works) makes browsing the web with touch often easy, yet very hard, when something is broken or nagging.
Quite easily: desktop SaaS web application; no Macs in the office and no interest in buying them specifically for iOS; no customers using Macs. Also, Safari works Well Enough (TM) for people not to complain about the minor CSS offsets and if they do they can always install Firefox. I don't work there anymore, but I doubt any customer will even try to switch to Macs in the next five years.
For my personal use cases: if my site doesn't work on Safari, I can't legally test it on any of my devices so I don't bother. Even Microsoft published a cross-platform browser, I'll care about Safari the moment I can apt-install safari-dev/winget install safari.
> Funny, iOS tends to be upgraded further back (ie support older devices), and faster [2], than (say) Android [3], because Apple is aggressive about updating users.
Yes, iOS updates devices faster. However, Chrome isn't tied to the OS.
I've said it before and I'll say it again: my perfectly good iPad 2 is useless despite its quite competent CPU purely because there are no browsers for it. Had it run Android, I could just install Chrome and use it for slower but quite usable browsing; with the Safari lockdown the device became useless.
You can't install an up-to-date version of Safari onto iOS 15 because of Apple's architecture decisions, despite iOS 15 still receiving plenty of other updates, which means you're restricted in features if you can't install the latest major upgrade.
Google decoupled WebKit from the system image years ago and has always allowed alternative browser engines like Firefox, which means you can install the latest version of Firefox on Android 5.0 (November 2014) or Chrome on Android 7.0 (March 2016), but not Safari 16 on iOS 8 (September 2014) or iOS 10 (September 2016). My Oneplus One (April 2014) still browses the web fine, and it's a mere budget device compared to something like an iPhone!
E.g. in Germany desktop Firefox has roughly double the market share of Safari.
Not speaking for the OP, but the internal tools I work on only supprt Chrome - you can only login to these systems using Single Sign On, which is only possible to login via Chrome (Google SSO). Makes devving loads easier!