But you can extend things so much easier inside of a browser tab (Greasemonkey, etc) than you can with a native app.

I know this is a thing, but really…who does this? The last thing I want to do is spend time tweaking someone else’s web site (unless I am getting paid to do it).

Wanikani users apparently.

This is actually a solid counter-point. My concerns with browser extensions is that you can't necessarily trust them or find something you want done, but I concede that having the option doesn't require you to do anything, whereas a native app doesn't necessarily give you the option.