Safari, the browser that claims to support standards but always comes with caveats, like saying they support transform/transitions and then everything with box shadows flickering
My codebase is full of Safari version-specific bug fixes.
Other browsers are updated more frequently and do not need OS updates.
Safari users are left behind with a broken browser.
I have more iOS 16.1 users (specific version) than all Chrome users with 6+ months old versions.
Web push notifications literally took years to make it from macOS to iOS, for example. (Yes, these are commonly abused for spam and other user-hostile things; no, I don't think that's a valid reason to withhold them from the only acceptable browser on their OS entirely.)
They adopt new web APIs much more cautiously - or they drag their feet - depending on your perspective