Magsmay, yes, it's a respectful courtesy, but I suspect it's quite old-fashioned these days. A lot of people don't use their Mrs etc handles in daily life, I know I don't.
Indeed, in my professional context, I would wish to do the same...
Talking of which, the etiquette of putting qualification letters after your name isn't always followed - I have a colleague who puts X, MSc, BSc - I always understood that if you had a Masters degree, that takes precedence over the BSc (as a lesser qualification) so you don't need to mention the latter.