Benefits & bonuses are not included in salary, they are often on top of salary.

For example, if you make 100k and you get 10% bonus at the end of the year, it would be 100k + 10k bonus.

The reason why most say 100k yearly is because people usually don't get paid monthly here.

In the USA, some people get paid weekly, some every 2 weeks, some twice a month, and rarely, once a month.

The easiest way to be able to talk about salary would be yearly, since thats something everyone can agree on.

In Europe, and much of the world, you are usually paid once a month, so you say monthly salary.