They might be trying to appease Google who now won't let you pass a recaptcha on windows because windows isn't locked down enough, and force you to scan a code with your Google phone instead.

> just so that grandma doesn't accidentally install malware

That's the stated reason. The actual reason is that they are salivating at the sight of how much money the app store and play store are making. They just don't want to move too quickly for fear of customers revolting.