I was recently asked by someone I very much respect to address "the" question. So I started to write the answer in a post... about five times without any luck. The "Why does a 20-something join a Reform Congregation" question.
In Haazinu, Moses recites a poem telling the people of Israel that they must give glory to God and be true to God whose ways are just. He instructs them to consult their elders and “remember the days of old.”