The more senior a member is, the more experienced and knowledgeable he is. this is like in the real world. So when he argues in a discussion forum he is expected to be a reference. different from new members, usually considered still amateur and can not be a reference.
Rank is only based on seniority but it doesn't mean that high rank members are more knowledgeable than the low rank.
Maybe some are more knowledgeable but not all of the high rank, based on how I evaluate myself, I still see that there are low rank that are smarter than me.