Yes - and those rules are there to be followed. If you arranging an event you can make whatever rules you want (everybody wear baby blue? :-)) But the key thing is this: Just because you can't/don't have time to/don't want to paint you should not be considered a less valuable part of the hobby. This can't be argued with unless you are very narrow minded and/or an elitist.
Let me use an example: Football (or soccer as they say in the United States) - everyone can enjoy and play it, but not everybody have the most perfect equipment and shoes (for various reasons). Is their enjoyment of the sport less valuable than a professional player (enjoyment not monthly paycheck)? Same thing goes here - if I just want to play a few games here and there and not think anymore about it: I am just as valuable as any hardcore hobbyist spending 120 hours on every model.
If we can't see beyond this - we will never have a hobby that is as large as it deserves to be because we are setting up way to high barriers for entry.
/M