Groups which lobby on your behalf without you knowing about it

Millions of Americans are members of the AAA, AARP, and other similar non-profit organizations. They join because they want to get the benefits they provide. Yet these groups lobby energetically in favor of what they see as their agenda - one which the members do not vote for, and may not even know about. The AARP has a position on everything relating to aging, The AAA lobbies against environmental control (as does the Chamber of Commerce). Yet most members do not participate in this. I have long wondered how this happens. Does this dilute democracy as much as corporate lobbying? Does this make the individual voter even less important?