The biggest thing from the employer side is that the cost of a single bad hire can be potentially enormous. This is a combination of legal (threat of wrongful termination lawsuits, COBRA) and cultural (nobody likes to feel like a jerk boss, morale problems among the remaining employees). The rule of thumb among managers is don't hire anybody unless you're 90% sure they'll work out for at least a year. That creates a…
I agree that this is a good idea, but the market won't accommodate this kind of labor change without government help. Employers have been able to shift responsibility for training off onto other organizations (i.e. coding bootcamps) to get individuals trained and prepared for jobs. Nowadays, workers themselves largely have to bear the financial burden of training in hopes that they land a good-paying job.
What you're suggesting essentially places the financial burden of training and skill development back on companies through apprenticeship programs. That's not going to happen voluntarily.