Google (and Amazon AFAIK) do give people resources to study with before an interview. Facebook sent me an electronic copy of CLRS beforehand.

I think the real question is: would making the interview process more accessible through offering courses increase the average quality of hires? Or allow more hires of the same quality? That's not clear. The actual white-boarding is pretty far divorced from day to day work, even at BigTechCo. An argument could be made that self-driven prepping for an arbitrary filter is the actual thing being tested, since it correlates more with success. Courses, although reducing the noise that comes from differing levels of prior exposure to those types of questions, would simultaneously decrease the self-motivation signal.

You've seen the interview process for Amazon right?

I mean, it's like they're trying to eliminate all human beings from consideration, before they even get started.

I imagine a couple of things work against this; nobody wants to take the pride hit of working for a small sum of money for awhile. Perhaps they imagine they'll have another high-paying job in a month so it's silly to take low pay for 6mo and HOPE the high paying job comes in after that time. Also, what happens if they can't hack it? Suddenly they probably can't even claim unemployment...

It's a good idea, though, it probably just has a few practical barriers.

There's no incentive to do this. Amazon/Google aren't exactly hurting for SWE candidates because of their brand.

That's a good idea. Like a boot camp for experienced people to get up to speed with the latest stuff.