Like this author I also suspect the shutdown has nothing to do with money and all to do with strategy...
Romantic words but: are you sure the shutdown reason is lack of financial success? What are other explanations you can think of?
Lack of revenue should be interpreted as "lack of facebook-esque" revenue. I'm not suggesting they couldn't be running a nice, stable business. But if the service is being shutdown, it is very, very likely they weren't seeing the growth numbers they would expect at Facebook, and that the team's engineering talent could likely yield much higher returns if deployed elsewhere in the company.
I don't buy it. Even if Parse's contribution to FB's bottom line is/was less than a dent I would still run other options before shutting down. Maybe keep the technology/team but sell the product? As you rightly suggest even keeping it running as an educational tool makes more sense than closing shop. Something else is going on...