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?
Wwll, I get 14 monthly payments a year, so two times a year the double amount, plus a yearly bonus, plus a fixed one time payment, so monthly would simply not represent how much i get yearly.