This is all, of course very fuzzy, but "I will spend 30 dollars on food tonight" can turn into "I call the restaurant and order 30 dollars of takeout" vs "I use door dash to get 30 dollars of food from that restaurant", and in the latter the restaurant sees less sales. But if I'm already like "I will have food from this place I like" and it's not on doordash or w/e, I might still be motivated enough to head over there!
There's a lot of dynamic variables here (including of course the "the person doesn't order from the restaurant"), but the few times I've used those delivery apps I end up ordering very little food for a lot of money.
While I won't go as far as to say that Dominos & co. are trying to run delivery entirely at cost, it is not clear to me that delivery from a shop directly vs delivery with a middle layer (having to pay lots of engineers fancy salaries mind you..) is an equivalent operation.
Remember, delivery apps take the costs and then their cut. That cut theoretically has some pressure from markets or whatever, but ... well.....
There's a lot of dynamic variables here (including of course the "the person doesn't order from the restaurant"), but the few times I've used those delivery apps I end up ordering very little food for a lot of money.
I try to just do takeout instead.