In a highly mobile labour market training people makes no sense. A trained workforce is a commons, and what we see is a classic tragedy of the commons.
Consider two firms with a budget of $100,000 for an employee for a year. Firm A decides to offer wages of $50k to an untrained worker and invest the other $50k in an intensive 3 month training program. Firm B decides to do no training at all. Worker joins firm A, benefits from the three months training and then immediately quits to go pick up the $100k salary for the rest of the year.
Generic job training is an investment, but, there's no way to get reliable ROI on it unless the training is super firm specific (like training in your own trade secrets). So nobody trains and everything is pushed onto the employees themselves via universities and trade schools, because that resolves the tragedy of the commons.