It's where the money is. Online food delivery is growing ridiculously and still have tons of room for growth since it is following the growth of smartphones and the rise of "online taxis". It isn't just food delivery. Grocery delivery, liquor delivery and all other delivery services haven't caught up to smartphone/online taxi service yet.
It's similar to what amazon did with their AWS. Most of their servers were idle. So why not turn that unused capacity for productive use. If you think about it, most taxis ( even online taxis ) are in idle state. So why not use that idle time for delivery.
Also slogans from large corporations or people working for multinationals are just PR nonsense. "Do no evil", "fair and balanced", "just do it", etc are marketing PR rubbish. Steve Yegge, like alphabet, is in the business of making money.
Cancer research is high risk/high reward. Food delivery is low risk/high reward.