Panel interviews have the advantage of looking for a candidate that can display all of the competencies required, the fully rounded candidate, not just good at one area (like getting on with people) but can work in (or lead) teams, solve problems, deliver results, communicate well, and has the relevant specialist knowledge.
If the hiring manager isn't involved, does rapport still matter? I think it does. Even though the interviewee wouldn't be reporting to us, we still want to get a sense of how well you get on with others and with us. Getting a number of viewpoints on one candidate brings balance to the decision making and gives a chance to a candidate who has relevant experience but just didn't click with that one interviewer in the style of interview you mention in your question.
Some of those more structured interview include the hiring manager, some do not. Where the hiring manager is involved, some thought can be given to how the person being interview would fit into the existing team. One of the most frequent comments I hear back from hiring managers after interviews is how much they appreciate the different viewpoints and the balance that is brought to the process.
The lists and tick boxes you mention, the competencies and their definitions, help candidates in framing their answers and interviewers in judging those answers. It's a shared set of criteria. Structured interviews help us minimise bias. We are human beings however and it helps if we like you!