My experience at a few start-ups has been that account deletion just isn't prioritized. It's not a focus when building an MVP. If the application ever gains traction, everyone is then terrified they'll accidentally delete customer data that they never delete anything. It's a shame. As a user, when I delete my account or data in my account, I want you to permanently delete it, not keep it around and just make inaccessible to me.
If it makes you feel better, the startups that don't have time to delete your data probably don't have a viable disaster recovery plan either.
As we learned from the Atlassian snafu, even giant companies with billions in revenue often can't recover from disasters. (I try to test mine every 6 months.
I've never had a test go perfectly.)
I've also seen businesses retain "deleted" data in order to support legitimate data analysis work in the future. And it actually can help significantly. Maybe scrubbing PII from deleted accounts is a good idea, but those deleted accounts are perfectly good data points, especially in smaller/newer companies with lower-volume data streams.
If you want to retain anonymous statistics, fine. I'm not keen on you retaining my actual data so you can monetize it after our business relationship has concluded. The biggest thing a small team can learn is why they failed to retain a customer or a trial that didn't convert. For that, usage metrics are considerably more valuable than user data.
