Katie wrote:"Why is it so common to not put the salary on job adverts?"
Because they want someone highly skilled who is willing to dedicate themselves to the company and make a long-term commitment. And the first act of this mutual respect and co-operation is them picking the applicant who asks for the least money.
One of the reasons I like where I work. When I started their first offer was above my stated required salary. They said 'you're asking for below the minimum we pay for that position' Then bumped me up another 5k above the minimum based on experience. We don't keep the talent we need in order to succeed by low-balling. Especially not when there a dozens of other opportunities in this city, all of them hiring. (Now Amazon on the other hand, THOSE guys have a reputation for brutality. Low balling, and then throwing you away in a couple years when they can replace you with a 1st year college grad who'll work 70hrs a week for 1/2 the salary, just to get in the door).