The point is the scale of poor people vastly outweighs the scale of Neuralink users. It's not worth both the setup cost, nor the backlash to convert the relatively small number of Neuralink users into forced labour. Especially since they would still need the poor workforce as well.

Agreeing to data collection and sharing of your brain activity while concerning for it's own reasons, is not the same as forcing them to complete Mechanical Turk like tasks.