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?
Here in Canada, your income is denoted and discussed as hourly if you have an unpredictable schedule like shift work and annually if you work steady hours all year like in an office. We call the latter a salary, the former is a wage. You’ll usually get paid every 2 weeks or twice a month on set dates in either case. Hourly employees don’t get paid every hour, salaried employees don’t get paid every year, it’s just the units discussed in negotiation.
If you are talking to someone and they say how much they make it’s obvious from context whether they mean hourly or annually. $25 and $60,000 are very obviously hourly and salary respectively. If not, asking takes a couple seconds and isn’t rude.
Why annual salaries? Because culture is confusing mess and everything we have today stands on piles of chaotic history. Maybe saying big numbers sounds cooler; fashion drives culture more than any practical reasons. Asking why any culture does anything is an exercise in sanity, and any answer is a guess, especially here.
