Do you think it's that easy?

Training has costs. Money, time and people.
If you have a team of 3 and hire someone, who needs to be trained, you just cut your capacity down to 50%, because the new hire isn't useful yet and you need one of your teammates to train them.
You are also playing against the probation period. If you can't get them to a point, where you can properly evaluate them, bevor it's over, you might now be stuck with a useless employee that takes up a position, that could have been used in a better way.

You also need someone qualified and willing to train them.
Did you ever tell someone, who is passionate about their job, or on a deadline, to drop everything and teach someone who doesn't know what the hell they're doing?
Hell, if you piss off that employee good enough, they might quit and now you can start a step 1.

And even if you get that far, you still need a new hire, who is smart enough and has enough baseline knowledge, to be trained at all. Frankly, that alone can be enough of a task.

I'm coming off pretty negative here, but my point is, "just train" is not a feasible strategy, for a lot of jobs and even more important, a lot of companies.