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 not standard for me. We only talk about monthly numbers with my colleagues and friends.
For the US, but going by this thread it’s not limited to here.
Also, for what it’s worth, I would think if op was in a place that used monthly as the standard they wouldn’t have posted this complaint. If that’s not the case I’m confused by the point of this post?