What is it with light aircraft?

1. You don't have to be a member to participate. Much of the site is open to non-members with just basically organizational business forums being off limits to non-members. Special Interest Groups are so small that they wouldn't turn away any interested modeler, whether a member or not and regardless of your country.
2. You never said where you are from; since this is a US based model magazine, I assume USA when no country of origin is stated. The SIGs will lean towards US civil aircraft because many members are American and you build what you can get or see.
3. Foreign membership is $30 or $32 and includes a 12 month, 6 issue subscription to the Journal magazine, but again joining is optional. 

Trouble with that, Rob, is you have to be a member to get much out of it and it is very US biased.

I'd rather spend my limited funds on modelmaking, rather than endless club subscriptions.

But thanks for the heads-up.

Several Special Interest Groups that focus on non-military aircraft listed on the IPMS USA website.

http://web.ipmsusa3.org/sigs