Huh? Cashback cards on VISA/Mastercard have all but disappeared, I think Lloyds still do one but it has a promo of 1% for the first year then drops to 0.25% after. American Express will give you 0.75% on first 10k spend then 1.25%. 2% is unheard of (unless it's promo or heavily capped).
It's not just the WebKit bit, basically the entire app implementation is actually shipped as a "Private Framework" which lives outside the .app bundle. e.g. on macOS
% otool -L /Applications/Safari.app/Contents/MacOS/Safari
/Applications/Safari.app/Contents/MacOS/Safari:
/System/Library/PrivateFrameworks/Safari.framework/Versions/A/Safari (compatibility version 528.0.0, current version 623.1.14)
/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 1356.0.0)
There's a bunch of other private frameworks (SafariCore.framework, SafariFoundation.framework, SafariPlatformSupport.framework, SafariShared.framework, SafariSharedUI.framework, SafariSwift.framework) as well. I haven't checked but I assume it's similar on iOS.
Barely supported by Apple these days - in addition to needing to disable SIP which is a pain, it was broken causing system freezes for several major macOS releases.
QuickTime for Windows existed long before then, and Apple ported a bunch of the old Classic Mac Toolbox to Windows as part of that.
IIRC it was actually this Windows port of Toolbox that in some ways laid the foundation for Carbon - i.e. a port of the Toolbox API to what became Mac OS X.
I wouldn’t hold not being on the Mac App Store against it. The MAS is sort of a failed ecosystem with very low usage/engagement, and all the downsides of the iOS store like potentially lengthy review times (can be a lot longer than the iOS store since it seems to play second fiddle) and arbitrary capricious rejections when you’re just trying to ship innocuous bug fixes to users.