I used to go to SXSW interactive most years, and one of the things that baffled me was why the conference had so many low quality panels - literally hundreds of sessions with 5 speakers and evidently very little preparation.
Then a friend pointed out that the primary purpose of a panel was to get companies to pay to send those five people to Austin, TX so you could hang out with them and have conversations.
That really clicked for me: the goal was to get a large number of (hopefully) interesting people in one place. It wasn't really about the content at all.
There are exceptions but panels are often pretty bad. As you say, often not well-prepped. And if it's sponsors, everyone has their talking points and everyone is probably going to be nice and polite to each other. Panels can be good but it's not the norm.
Then a friend pointed out that the primary purpose of a panel was to get companies to pay to send those five people to Austin, TX so you could hang out with them and have conversations.
That really clicked for me: the goal was to get a large number of (hopefully) interesting people in one place. It wasn't really about the content at all.