From a shops point of view, aprents can be time consuming for little gain.
Most want to be rebuilding engines on day 1 and could not be bothered demonstrating they know the basics (what they are there for in first year). Crap pay but as stated they leave after so long, so all the investment in time and risk is eventually wasted.
A good apprentice is worth their weight in gold, most are a waste of time and so they all get treated that way. Get rid of these without a drive to succeed in the first year, then start teaching those that make it to 2nd year.