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?
Agree. What a weird thing for op to be upset about. I have never once in my many years on this planet had someone confuse an annual salary for a monthly one.
Annual pay is the standard if you work full time. It's definitely not a rich person thing, it's for taxes, total takehome, budgeting, you name it. In fact thinking about it, I think it'd be more work for me to figure out my budget if it was monthly.