That doesn't quite line up with what you said earlier on when you quoted something you found online about all of the kitchen staff duties the delivery driver purported to perform and you said was therefore deserving of a tip. When I questioned how a dine in customer should intuit that a tip should include an amount sufficient for several back of house employees you said that customers simply didn't realize that was already happening with their tips. Your comments seem to be taking slices from both ends of the loaf.
When I refer to kitchen staff, I'm talking about the line cooks and chefs specifically. The ones whose primary jobs are cooking. Those people have never been included in the tip pool in any place I've ever worked, and as they aren't regularly interacting with customers, a restaurant owner here in the U.S. would be pushing the bounds of legality to include them in the split. Not to say it
doesn't happen, because pushing the bounds of legality is something the restaurant industry excels at.
There are also legal issues with managers including themselves in the splitting of tips, but it's not uncommon for that to happen anyway.
The people whom I was referring to in my earlier comment to you was the "back-of-the-house" employees -- bussers, barbacks, food runners, etc. Those people are regularly part of the tip pool because, since their job duties do require them to regularly come to the front of the house where they're visible to customers, employers can consider them as having regular customer interaction and apply the tip credit to them. (Tip Credit is the term for being able to legally pay someone less than minimum wage with the assumption that their tips will make up for the rest.)
Regarding the article I linked, I remember the guy saying something about proofing dough (and maybe a couple of other food related tasks) but he also listed washing windows, taking out trash, assembling boxes, etc. The point of that was to show that a driver does more than just drive pizza around and walk it to your door.* That some of his duties are kitchen related is not surprising, there's a lot of overlap among job positions in a restaurant, but I don't recall him saying he was primarily responsible for making the pizza. I assumed there was a separate staff for that, and it's likely those people make minimum wage or more and are probably not included in the tip pool. The two employees working the counter, the one who answered the phone, the six other drivers on shift that night... It's quite possible they are all sharing in on the tip you give to the guy who brings your pizza.
*Should it be a customer's responsibility to help compensate an employee for all the work he does behind the scenes above and beyond delivering the pizza? No, the employer should be responsible for paying the employee. But, since restaurant employers are not legally required to pay a living wage, personally, I do take into account the work that happened behind the scenes when I tip. No one's required to do that, though, and may choose to only tip based on the effort it took to walk the food to the door. That's fine too.
