Yeah…Honestly now that you mention it I never have looked into how they’re structured and if that may play a part in them not doing so. What I do know is that I respect their mission and want to see them stick around and reshape things to allow for more organizations like them to exist rather than get snuffed out.
In some respects it was somewhat easier to get them to be on multiple platforms instead of moving. Think of the original messenger proliferation, where sometimes people would be on IRC, XMPP, AIM, ICQ, MSN Messenger, or etc. so much so that you had software like Pidgin and Trillian to help consolidate server/chat rooms and friends lists to more easily chat with all your contacts.
Even with Ventrilo, I remember being open to also switching to Mumble or vice versa if there was some hiccup with either.