How much of H1B hiring is because companies want to pay people less and how much is it because there genuinely aren't enough trained people to do the jobs? I a

How much of H1B hiring is because companies want to pay people less and how much is it because there genuinely aren't enough trained people to do the jobs? I ask this question because I don't have any exposure to h1b hiring, so I really do not have any sense for what really goes on. It sounds like these programs get abused, but there is a lot of noise out so I can't be sure.