For example, making a pizza is what, 10 minutes, or less, when adding up all the labor involved in a restaurant setting.
In comparison, taking said pizza, even around the block, with the courier having to arrive take it somewhere, is I'd estimate at least 15 mins.
Someone has to pay for that human labor, and considering how expensive it is, and not only that, VC funded food delivery startups want to take a huge markup on that. Something has to give. Crap wages for couriers, restaurant staff, skimping on raw materials etc.
It's much better for everyone involved to cut out the middle man, have restaurants on every corner (considering in most apartment blocks, nobody wants to live on the ground floors anyways), with the upper floors used for apartments or offices.
This is hardly an original thought, tons of European cities I've been in do this.