TL;DR: it's a relic of the 19th century, when the two professions were largely distinct. Today: it's a flex by the "gunners" to somehow distinguish themselves

TL;DR: it's a relic of the 19th century, when the two professions were largely distinct. Today: it's a flex by the "gunners" to somehow distinguish themselves as better than "lesser" physicians. A similar thing occurs in the US, it's just that some physicians, in addition to a preceding "Dr.", follow their names with even more letters/affiliations. I only attended one year of a US medical school, but the surgeons were at a whole 'nother level (in this competitive exercise of perseverance)...