There are many reasons, but I will give you an example that hasn't been explained yet. For some work, there is a set hourly rate the company can charge. For i

There are many reasons, but I will give you an example that hasn't been explained yet. For some work, there is a set hourly rate the company can charge. For instance, they may bid a contract $50/h for each developer. In this case, I can pay a mid-level developer 65k/yr with 35k/yr in benefits and overhead, and break even with $0 profit. If I hire a more junior developer and pay him 50k and train him on the job, I then make 15k in profit and he gets a year of experience.