I think the owners are tired of giving up so much control - your proposal sounds too similar to the platforms they are trying to leave.
Without having the first-hand knowledge of parent comment, my assumption is restaurateurs want more control of both the marketing and the delivery process. I don't think there is enough $ in the pie to pay a third party for marketing and a 3rd party for delivery. I believe the desire is to go back to something they can more directly manage (traditional delivery worked for them), but have an online ordering/POS tool that is easy to use/find from a google search. The consumer does not care if the order is delivered by an employee or someone on a network.
The cost of using drivers between restaurants has to be cheaper than each restaurant having it's own exclusive drivers. Labor is a huge component of restaurant costs, and having idle hands is bad. It's no different than time sharing.
There's no reason they have to use a third party marketing company, if they want to build their own menu and run their own ads.
Without having the first-hand knowledge of parent comment, my assumption is restaurateurs want more control of both the marketing and the delivery process. I don't think there is enough $ in the pie to pay a third party for marketing and a 3rd party for delivery. I believe the desire is to go back to something they can more directly manage (traditional delivery worked for them), but have an online ordering/POS tool that is easy to use/find from a google search. The consumer does not care if the order is delivered by an employee or someone on a network.