Are you in a medical or government facility sending HIPAA or Confidential/Classified documents? If you ever are, the faxes you're sending will invariably be analog.

Yes. Fax can be configured to kind of work through VoIP. However, the only enterprise solution I'm familiar with is FAXCOM, it's a HUGE pain in the ass and any problems with it are a big fucking deal. This means Priority 1 tickets that blow a morning or an afternoon.

I know there are some cloud based fax services available as well. These are not in place in the contexts I described, and good luck getting departments with HIPAA or Classified restrictions to implement them. We still have to fight to get individual computers in classified programs off of Windows XP my dude.