Some are good. Others are just not helpful for most of their members. First, the make-up of the committee is critical, and probably overlooked. It would be remarkable if a golf committee reflected the full range of the playing abilities of the club membership. If it doesn't, there will likely be problems with the committee's results, if not supported by appropriate statistics.
Human nature explains the problem.
It is hard for people to refrain from emphasizing their own personal experiences when asked to make decisions affecting others. For golf committees, it is especially difficult to keep the entire membership in mind when asked to rank the 18 holes of their home course. Their task is nearly impossible if they have no basis to rank the holes other than their own playing history. If either duffers or scratch golfers dominate the committee, their choices will most likely fail to meet the needs of all members. This failure may not be intentional, but it is a likely result.