I'm guessing someone looked at the data and figured that losing x% of users is worth it if they can extract an extra y% profit from the remaining users. We'll shortly see if they are right!
If I was in their position, I would just restrict 3rd party app access to Reddit gold subscribers. You would probably lose less users that way, and extract at least some money from them. You'd need to figure out some heuristic to detect when people are "abusing" their reddit gold to scrape all data. And also work with 3rd party developers to reduce the number of API calls they make rather than just being condescending dicks [0].
If they did all that, they could probably even milk it a bit, something like: "We heard the community and we are listening!".
[0] https://old.reddit.com/r/redditdev/comments/13wsiks/api_upda...