I revisit this question from time to time myself and while I would love to switch across to email entirely, there are a couple good reasons to keep using a technology which goes back to 1843, especially in this digital and connected age? Leaving aside the fact that sending and receiving a fax has changed over time to the point where we can do both digitally, why would we continue to use faxes?
The one thing which comes to mind immediately is that you receive a fax transmission report when you send a fax and that is a big plus for faxes. As far as I know, there is no universal delivery confirmation report for email (unless by “universal” you mean Outlook users) which is issued irrespective of whether the recipient wants it to be issued. That report is important if having confirmation of their delivery is essential. A good example of such an instance is the transmission of notices in terms of agreements or some legal requirement.
The drawback with faxes is that you usually have to have a phone line handy to send a fax (although I understand faxes can be sent via email in a similar way that they can be received by email although I haven’t tested out a fax by email transmission yet). Faxes are also pretty limited in that you can only really fax something that can be printed out. You can’t fax multimedia files, for example.
There are probably quite a few more pros and cons to using or ditching ye olde fax machine that you have come up with yourself. While I would love to ditch my trusty fax service, I suspect they will be around for a while longer, at least until that universal delivery confirmation facility becomes available everywhere … At least, that is what I am waiting for.