That doesn't follow at all.
I get it doesn't sound great. It isn't, but still true.
In fact they supply negative value, they sever the retailer>consumer relationship and they're highly unlikely to (for instance) handle RMAs etc, while charging higher prices. They exacerbate shortages by taking a chunk of the supply.
Think about it this way. assuming the main issue is shortages, not scalpers. Then most people wouldn't get a card anyway, because there are just way too few. if they're desperate, they can't go to a retailer and offer to pay more to get one. But they can with a scalper.
So, scalpers only exist because some people are willing to pay the crazy prices to get something they can't. That's the 'service' they offer, and that's the only reason they exist.
My argument only fails if scalpers are the main reason you can't get cards. I don't think we're there (yet).