I'm an engineer. Typically I interviewed with various disciplines and bosses. Lunch was usually a softball interview to make a candidate more comfortable. The last interview I had, I was considered a high value interviewee (not sure if I deserved that) but it meant I was asked to give a presentation during lunch. It can be pretty brutal honestly. Some places are worse than others. I heard that Google and Agilent would sometimes ask candidates to solve equations. There's no way I could perform like that in front of people.

To bring it back to the topic, I do think it would be a bad look to bring in a Starbucks to the interview.

In my previous job, we interviewed people for several positions, usually 4 to 6. Each area was looking for different things, so multiple interviews made sense, then it was up to each area if they wanted to make an offer. We'd include break for lunch and get non-managers to take them for lunch so they could chat. So not one 8h interview, several one hour interviews. This is pretty common with large organizations.

I had all-day interviews for my job too, including lunch. For me, they were already pretty sure I was the right person to hire, so it was only the one round of interviews. I was even a few minutes late due to my employer having several buildings and the one the interviews started in was unmarked. I showed up early to the wrong location.

That being said, while a single round of all-day interviews isn't bad, it would really suck if you had to do that multiple times, and would likely be a waste of time for everyone involved