Many already mine PI via mobile, but PI limits the KYC system. Creates limitations on PI users. And PI only runs on the PI blockchain system, it cannot be moved to a different platform.
The reason the KYC system was created was because it was so easy to mine PI on mobile (anyone can install the app, and apparently it was even possible to defraud the system by creating many app instances.
And this is the problem with this type of idea that you "mine" a blockchain easily by making the phone the node. Makes it easy to cheat and then forces the owners to KYC.
Pi was always going to be a failure the moment they needed people to refer to "earn" and "secure" the "blockchain".