It's quite a bit of effort, as well.
Some users are doing it, but most seem to be happy taking the easy money, even if it's less than you could get hustling for your own sales.
The main benefit of this "side gig" is the lack of time it takes. The amount/hour it pays is silly... once you start putting in serious time to making it happen, well, yeah, you make more dollars, but your dollar per hour goes way down.
It may still be more than you make elsewhere though, and worth it to you, but many of us are just collecting the extra easy money, and happy with that level of it.