I think a club is simply an extension on the web site.
While there may be the benefits of club registration for vehicles, it may also offer such things as an on going newsletter / email with up coming events etc.
While the website can offer almost instant and numerous answers to questions I think that the club side would be a more social side to the passion.
This may in fact enhance the website with people gathering in larger groups of utes and vans attracting more interest and maybe drawing more people to the site.

Clubs are not for everyone, in fact my experiences with them have been less then pleasant, however I did meet more people with similar interests and learned a lot from their experiences.