I don't think it's got anything to do with rules and regs! It's just a lack of interest...... I'll go out to a khana or track day with mates just for a look and the same thing happens "this looks like fun", "Matt help me build up a dato"....Do they do it? NO! Loads of money just couldn't be bothered! I did an event every month when i was an apprentice, I had a 180b sss painted matt black and was cheap. You also only race the clock so half the fun / reason is to improve on your own times! Haven't done an event for about 3 years but as i have just finished restoring my car trailer i'm gonna get back into it! As L18 has said its called club level for a reason... You could do a year for about $1000 which is only $20 a week (a dole bludger could do it). I'm in a club called the north shore sporting car club
www.nsscc.com.au which is heavily into rally but also runs club level events as well as invites to all the other events run by clubs all around sydney. You don't have to be in a club to go and watch! While your there speak to the competitors and officials and you'll soon learn that its all about low cost, fun and safety.