People may still use fax because it is simply more professional, depending on the business and preference. We find that many people still use machines and may need the printed document. So, while it is convenient for RingCentral users to fax via email, the recipient may not prefer email and use their machine.
It is sometimes much more convenient to use a dedicated fax machine. WIth a fax, you simply put the documents you need to send to another office into the fax machine, dial the number, and come back later when it is done. To send via email requires you to first scan the documents; then, assuming you have a well-running network, you have to retrieve scanned documents from the scanner, put them in an email, and send it. If you are doing this by scanning to a USB memory key or some other portable media, forget it. The fax machine wins hands down. The only way the email fax wins is if you happen to be away from the office and need to get a fax on your phone or something.
In this case, I concur that traditional fax is still more reliable compared to email and electronic fax. Not to mention that there may also be users who are not tech-savvy and may grope with the electronic menus. Still, it is nice to keep up with the ever-changing technology.