Some iOS developer correct me if I'm wrong

1. Safari supports extensions

2. WebView, the thing most browsers on iOS are required to use in most places, does not directly support those same extensions. In other words, there is no simple options to allow the same extensions.

In other words, Apple makes it harder for alternative browser to support extensions by requiring them to add their own support. That wouldn't be an issue if Apple allowed alternative browser engines but since they don't (in most places) then it's arguably an added hurdle.