Based on the users that use our dating web app - about 10% of our revenue comes from the Samsung browser. Which says to me that lay people can't be bothered to use anything but the default "productivity" apps that come pre-installed on the phone. It has "Internet" so installing Chrome doesn't matter to them.
Samsung's browser is complete garbage too. It's the IE of Android and I hate supporting it.
It's certainly a pain to support ... I get quite a few compatibility / layout issues with web sites. However I use it anyway because it has a bunch simple incredibly obvious features that for my use make it infinitely better than Chrome for simple browsing.
I actually liked when chrome tabs showed up in the app switcher... I don't like FF much at all, but I at least get ublock on it. So FF is my default (so launches from twitter/fb go there), but the sites I go to directly, usually done in Chrome.
The main one is simple but effective bottom navigation functions and quick access bookmarks. Stretching up to reach the navigation bar on a large phone is almost impossible one handed in chrome but easy with the Samsung browser.
I wouldn't be so sure that people who use it don't bother to use anything else. I use the default Samsung browser because it's simple, clean and just tends to work for my better for me than chrome, especially since I don't tend to use it very often. For other apps, I prefer google or third party apps over Samsung any day. I try to stay away and disable most of the Samsung apps that come on my phone since most of them just work poorly and tend to be very annoying.
Samsung's browser is complete garbage too. It's the IE of Android and I hate supporting it.