Don't blame IPMS for the lack of car builders or for them to be rather dismissive about car modelers. It is the lack of car builders in IPMS that has led to us being second rate citizens, until we get off our butts in gear and do something about it.
The San Diego IPMS has a yearly show and the car portion was always a bit dismal and not very well judged, until the San Diego Model Car Club joined in and now runs that part of the contest.
Yes, the club had to join IPMS and only the officers, and maybe one or two others, are members, but it was us speaking up and joining that changed some attitudes in our local IPMS. And it goes back to the cheapness of the car builders. Most do not want to pay dues for anything.
And I know plenty of deep pocket, anal retentive detail freaks who are car builders. So that goes both ways as well!