The "drag it to Applications, move to Trash to remove" flow was invented decades ago, possibly even back in NeXTStep [0]. Application bundles are not meant to be writeable, user data cannot be written there. If Apple envisions a future change, they’re really terrible in implementing it.
I suspect Apple has little incentive to fix it since if an app stores a bunch of data in ~/Library/Application Support and then you Trash the app, then your 256GB SSD (still standard even on a 'professional' laptop, in 2025) is that much more filled, eventually prompting you to curse yourself for not spending $400 in nearly-pure-profit to upgrade that to 1TB.
[0] https://www.nextcomputers.org/files/manuals/nd/Concepts/Inst...