[twayt]

This is a pretty simplistic take tbh.

Reddit makes money from ads having reach and they're hoping that only a small percentage get premium so that they can continue to make money off of ads.

Why would they reduce the reach their ads are having by making it easy for people to opt-out?

Their API pricing probably reflects the money they are losing by not getting the users on their own platform and showing them ads.

Their hope is that people would switch over to the main app so that their advertisers can pay them more.