RSRs [1] are sort of not this though. They’re still a bit weird, but can contain updates for WebKit and/or Safari in a very small update that installs very quickly. Also worth noting that WebKit is buried pretty deep in macOS (as it underpins a lot more than just Safari) so isn’t as easy to patch by itself.
They might also see it as an incentive - perhaps new app features act as driver for OS adoption.