I'll admit I haven't seen a lot of explicit on-the-job training (besides that dealing with internal technologies), but I have seen a lot of people who's first job is less challenging than their later ones, who use it as a growing experience and a stepstone.
The real question is whether a large number of programmers don't reach their full potential or do so significantly later than they would have with proper mentoring. A difficult thing to find evidence for either way.
I'll admit I haven't seen a lot of explicit on-the-job training (besides that dealing with internal technologies), but I have seen a lot of people who's first job is less challenging than their later ones, who use it as a growing experience and a stepstone.
The real question is whether a large number of programmers don't reach their full potential or do so significantly later than they would have with proper mentoring. A difficult thing to find evidence for either way.