I think this is mostly a US thing. Why use yearly salary? You’re not paid once a year, are you? Most likely once a month. Referencing monthly salary makes much more sense.
“I’m making 50k”. Great, now I have to guess - dollars? Monthly? Yearly? If yearly then what’s the monthly paycheck? Net? Gross?
Until you have people who get a yearly bonus. Or 13 or 14 monthly salaries a year, which is quite common in Germany (basically a bonus, but the employee is entitled to it).