For certain definitions of huge.
For me, nothing is worth creating an account on any Facebook owned service. I would like to be able to converse with its users whilst appearing as something of a black hole to WhatsApp. This is not and, almost certainly, never will be possible. Therefore, a unified client is something (which I proposed here Best All In One Messenger: Voice Calls, Video Facetime, Send Text & Attachments - #41 by Vaughan) whose benefit lies in its uptake by WhatsApp (and Telegram, Viber, WeChat, etc) users and their willingness to create accounts in it from non-invasive services (Matrix, xmpp, etc,) not in the willingness of users of the latter group to use it to create accounts with WhatsApp et al. After all, nobody here should forget the title of this thread 
Edit: Just to be clear, Matrix bridges are equivalent to people like me creating an invasive-service account in a unified client.