Self-driving vehicles are not only here to solve food delivery.
In the US, the average American spends about 365 hours a year driving, about an hour a day.
I'd much rather use that time to work, read a book, or a dozen other activities. It's over 6% of my waking hours.
There are at least 3 different app based food delivery companies (uber eats, skip the dishes, door dash) in the city near me, on top of the fact that a lot of places have their own dedicated delivery people (Grocery stores, pizza, even liquor stores)
There's clearly a competitive market in this space.