Email vs. Fax
Rewind history to the 1980s when dial-up modems
started at 1.2 kbits/s and peaked at 9.6kbits/s (chart
)†. Some email
was basically instant messaging, requiring both users to be dialed-up at the same time. For email which did not require this, there was no notification that one had received email prior to dial-up, leading to phone calls asking "Did you get my email?". In contrast, you knew exactly when you were getting a fax. Email originally only allowed character transmission, while fax could do pictures. Email required much more set-up than a simple phone number.
† In comparison, the older-generation 3G standard for mobile [phone] data has data rates
of 384 kbits/s for driving and 2000 kbits/s for stationary/walking. LTE increases speeds by 150x