Hi, English isn’t my mother tongue so I was asking myself that question since I first encounted a w/… Back then I was like: “What tf does ‘w slash’ stand for?” And when I found out I was like “How, why, and is it any intuitive?” But I never dared to ask that until now
Except Dr., Mr., ie., etc. use a period.
Both versions exist: https://en.m.wikipedia.org/wiki/Doctor_(title)#Abbreviation