iOS only allows PWAs in Safari, and Safari lacks a lot of features for PWAs - firt.dev/notes/pwa-ios/ is a pretty good resource for figuring out what they do and don’t support.
Outside of PWAs, Safari is a pain to develop for. Unlike both Firefox and Chromium browsers, its “dev tools” are a bit of a mess and don’t support simply adding extensions like React Dev Tools to augment them. To use such an extension you have to run it as an independent application and connect to Safari, and IME doing this it frequently fails to actually connect properly and didn’t provide a comparable workflow.
When I was working on an app that only needed to support Safari, I ended up just using those extensions in Chrome or Firefox rather than trying to build it in Safari.
And this is my experience building on a Mac. For anyone developing on a Windows or Linux device, it’s not like they can just install Safari locally to confirm that everything works. So if something doesn’t work in Safari, it’s probably not gonna get caught by the developer.