For a bunch of reasons: 1) he doesn't want the signal community to fracture with incompatibilities (like say XMPP) 2) he doesn't want the security of signal u

For a bunch of reasons: 1) he doesn't want the signal community to fracture with incompatibilities (like say XMPP) 2) he doesn't want the security of signal users compromised with less secure clients. Thus he's against SMS since it leaks metadata like crazy to 100s or 1000s of entities. 3) he doesn't particularly trust f-droid to distribute clients since they use a central key (an attractive target) instead of the developers key. 4) he wants to be able to quickly iterate improving the clients and server in sync, on his own schedule. So generally he wants to target a large number of users with a very secure client and doesn't want to sponsor anyone that takes his source with free server infrastructure. So he believes in audits, security, and opensource. He even will allow a GCM replacement, as long as it only runs when GCM is not available. He expects the battery life and user experience to be terrible. The main problem seems to be that google negotiates with cellular providers to not time out connections to GCM, but they silently do that (without an RST) to other connections. Thus any GCM replacement will have to spend much more power/battery maintaining a connection. Moxie specifically mentioned that even 50 seconds was too long and that some providers time out connections even quicker than that.