> Why would you want to enslave much people today, especially when half of them are expected to be of age 40+?

Likely because machines are single function and people are multifunction, you'll also need people to maintain those machines.

Then there is the less savory reasons.

You don't need that many people for tending to machines and you don't need that many people for "less savory reasons".

Even then, VR will eventually be as good for "less savory reasons" as the real thing.

Nobody would survive that with today's technology. This doesn't sound like a good idea to me.

It won't work this time. Cynically speaking, it's too expensive today per soul liberated.