Right, I think this is specifically marketed with people with steady jobs (either people with WFHable jobs like tech workers, or people who are going into work anyway like doctors and retail workers) who are continuing to earn their usual income during the lockdown. If you're not getting paid yourself, it doesn't make as much sense for you to be a buyer.
At least where I am, enough of the customers of independent coffee shops / food places / stores / etc. are people with steady, WFHable jobs that it seems like simply managing cashflow and making sure it gets to the right people is helpful in and of itself.
I don't have a good answer to the gig-worker problem (well, my preferred option is government-run safety nets; the other option is regulations saying gig employment should be disallowed, but those have their own problems), but I want to throw it out there for brainstorming. One potential option is the platforms offer zero-interest loans to their workers, e.g., "here's $1000 now, but we'll want $100 back per month when this is all over, if you continue driving for us we'll automatically take $100 of your earnings per month, if you don't you'll just owe us." Of course many platforms can afford to do that on their own, but they could also fund the program with gift cards from customers. That is, there are two levels of gift cards here, one from customer to platform, one from platform to worker.