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?
I mean, you just basically answered your own question. People get paid hourly, weekly, every 2 weeks, monthly, and some even per sale (ie. Realtors) so the only way to have a constant measurement is yearly.
Why not monthly? It seems the smallest unit to encompass them all, and is fairly standard.
Monthly makes sense also since most bills are monthly.
Most bills are monthly, most paychecks schedules are bi-weekly. To me this is the same issue as hot dogs and buns being sold in different quantities. Whyyyyyyyyyyyyyyy?!?!?!?!?!
Yes but a lot of work is seasonal and/or sporadic. Annual pay smoothes it out.
But most pays are fortnightly
Not here (the Netherlands), everything is monthly, both pay and bills.
Same in Hungary. Not a single person I know gets their salary weekly or biweekly. It's absolutely not a thing.
Also, your bills are monthly. You mortgage is monthly. Your credit card bill is monthly. Preschool is paid monthly. Everything is monthly.