1) Realm works only in React Native and not in React web. There is a regular web component to my project as well and the thought was we could reuse our knowledge of PouchDB across mobile and web. This has paid off in the prototype mode because it allowed us to build some simple reports in our web product. However, this is probably not the right architecture for reporting and we will likely change it soon.
2) Realm was very new and I felt we were already using too many new frameworks. So it was added risk on a tight timeline to get a prototype out the door.
3) On the server side, CouchDB has Futon to simplify our learning curve and give us a basic GUI to have a sanity check when our code wasn't functioning as expected. Not sure what Realm's server side looks like.
I'm sure I can come up with other reasons. But definitely want to check out Realm sometime. Looks like it is shaping up quite nicely.