It also means, if a critical mass hate developing on Macs, then iOS software will suffer. App store fees are already a business pain point for app developers. And web browsers are getting capable enough now that it's probably feasible for a lot of apps to go back to being browser only.
It's going to be hard to reverse a trend away from Apple if it starts. Imagine what would happen if Microsoft Visual Studio becomes the IDE of choice for iOS development after devs ditch macOS in droves. Microsoft won't play nice.
Apple isn't watching their flanks by letting macOS atrophy and a competitor will step in if they don't cover it.