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?
In France we often have additional months paid, 13 or 14 months, as an additional pay check in June and December. The monthly pay doesn’t account for that while the yearly one does. There are jobs also that have a variable salary depending on performance.