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?
It's pretty standard in Europe too. It's what you see when filling your taxes, but very often people have bonuses, over-time, 13rd month and other things making monthly pay not relevant