> It's not like sending an SMS to my phone is any more secure or harder to access than sending an email to my phone.
It's not, but much like 'fax' hanging on in the medical environment because it has been labeled "secure" by the regulations, there is a line in some regulation rule somewhere that labels "SMS" as "secure" but does not label "email" as "secure", and because they do the minimum to meet the regulation, they go with "SMS" and go on about their day.