Probably because all apps are now required to target the latest api, which means most permissions are done by user prompts, and not just by downloading the app.
I don’t want to download a clipboard helper of some kind and find out it’s going to ask for my GPS coordinates.
I want to know ahead of time.
An app may have permission to do something (e.g. access your location), but if the app's usage of this feature does not involve your location being sent to the app's server and stored somewhere, it does not need to be disclosed in the privacy labels.
Apple and Google cannot verify what happens with your data when it leaves the device - they rely on the honesty of developers to explain what happens.
This is a better approach for the goal, because if there's one thing they learned from years of offering the permissions list, it's that users can't convert the concept of "app permissions" into a good mental model of "What data the app can collect on me." They just aren't on average savvy enough. So the Data Safety info answers the question users actually care about without added complexity of pretending the average user is a developer who groks what permissions mean.
That sounds so much easier than just listing the possible permissions it might ask for on the Store Page before I install it.