This is an edge case in my experience. We're talking immigrants/expats that haven't learned the local language (I'm yet to see a restaurant hiring immigrants not knowing the local language for the front desk / phone duty). Not that it's not worth catering for, but perhaps not at the expense of everyone else.
> and hoping he wrote the right things down and don't make a mistake
This perhaps eliminates excuses. In my experience with on-line ordering, mistakes happen frequently anyway - it's not a communications issue, it's a "cooks and delivery people are extremely busy" issue. They'll just occasionally forget to add some topping or to package the extra sauce you ordered.
> and most important of all, ease of payment.
That is absolutely true. I was a fan of these third-party services because of that - because I could pre-pay using my card online, not bothering about having cash, whether the driver has change, or whether they took the card terminal with them. I was a fan, I no longer am, because mainstream food delivery services are abusive to restaurants and delivery workers.
> there is some value for restaurants, at least some of them, to not have to worry about hiring their own delivery driver.
Depends. Some may prefer their own drivers (e.g. small-scale restaurants, where the drivers are family members, or friends). Some purposefully offer no delivery (e.g. for branding reasons). The new breed of delivery services (Uber Eats, Glovo, etc.) don't give a damn about preferences - they'll offer delivery services for your restaurant whether you want them or not; they won't even ask you for permission. The problems here are twofold:
1. People associate delivery service with the restaurant. The squeezed, exploited drivers of Uber Eats, et al. make mistakes too, deliver cold food, etc. The customers often blame the restaurant. The restaurant suffers branding and monetary loss due to no fault of their own, and with no way of improving the service.
2. The business model of those companies depends on getting people used to ordering food from restaurant through them, and then blackmailing the restaurant into signing up and paying a percentage, or getting delisted. They're forcing restaurants into participation.
> If that's not the case, a disruptive service offering just a unified UI + Payment, but no delivery should have appeared by now.
One would think so, but this is a winner-take-all market; Uber Eats & friends outcompeted previous iterations of services that offered just the UI and payment service.