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?
Yearly, because over here some people get 12 salaries a year,some 13, some 14 and some even 15.
The yearly income covers that and also includes yearly or semi-yearli boni.