First, This requires users to setup this software. Then, there is nothing stopping them from working around or disabling it at anytime. If the software can’t be disabled then the user will switch to another product.
If someone is really trying to curtail their software addiction, actual dedication will be required, not just the activation of some tool that they can easily disable with a few taps.
And because these tools will likely not work for the majority of people, Apple and Google have every incentive to incorporate them into their operating systems and gobble up the market share (which they are already doing in their latest operating systems).
A more traditional and therapeutic approach to the problem makes more sense to me, though it won’t scale well and the market doesn’t seem very big