Companies try to maximize green per red. By paying less, and getting the same, they maximize that, year after year until (in a temporary and unforeseeable setback) you leave for... Bluer pastures, apparently.

There are different sorts of companies, and the more they think of employees as a number of years of experience plus a stack of skills, the more susceptible they are to believing that replacing humans with other equally skilled humans is a productive way to spend their time.