Well, it is essentially what they’re doing already with DRM.

Try watching a full resolution stream on any paid streaming service using “bad” software, like Firefox or Linux.

There’s no reason an app should be more trustworthy than the email.
It’s pretty standard for scummy companies to make the process as annoying as possible.

They already said they don’t want to.

They asked you to install the app on purpose, in hopes that you’ll decide it’s too much hassle and decide not to delete the account.