ASC supports the 18+ rule. Since, according to ASC community, those under 18 shouldn't have an AEG, then those under 18 should have no need for ASC parts.
Simple as that.
Oh, and Crunchmeister, in Ontario it is actually illegal for a minor to own an airsoft gun. There is provincial legislation covering that.
"Someone in a Prius tried to race me at a stop sign the other day. I couldn't believe it. I had him for the first 100 feet or so but I can only walk so fast."