What? There are many people who pay to use Christian's app specifically to interact with Reddit. If Apollo suddenly switched to another social network, it would make a lot of people understandably angry
Ivory has been well-received, but who knows what the numbers are compared to Tweetbot. So this was not a "just swap the API" slam dunk.
In Christian's case, if Reddit doesn't change their mind, his best bet is probably to eliminate the free tier, and increase the paid tier pricing. It's worth a shot, but Apollo would probably take such a hit it may no longer be viable as a business.