I've worked in IT type jobs for over two decades, in some sense training would help, but to be frank the code and systems IT folks have built are of such low quality that it's better for everyone if they're handed over to more competent teams that can cost effectively maintain them long term.
One reason why training is out of fashion is because of poaching. Companies don't want to invest a lot of money in training their employees only to have their closest competitors become the beneficiaries. That is a myopic view, to be sure, but it's a common one.
I think they do train people, it's just not formal. And the other issue is the companies have no clue what their doing most of the time anyway, so you just end up with IT people on the market will all sorts of nonsense opinions.
For when you can't find any more pretrained ones. Or to get someone for a lower salary and growing them that provides some loyalty and help solving the problem of not having enough pretrained ones in the first place.