I love that pic... is that you? That looks like fun!
As for the bit thing, I do agree, I start in a bosal, and rarely use a typical jointed snaffle, I hate them... another thread, anyway... as said then we go on to the curb... the IDEA is that your horse is so light you need only the weight of the bit to encourage the pretty vertical head carriage (the horse should let the headstall carry the weight of the bit) - and the reins also could be nothing more then a strand of hair, showing total lightness and obedience to the weight aids of rider and rein.... I can see that. Beautiful...
But it works with a heavy Bosal too! And my 4yr old does everything in her bosal she will be asked to do in her curb, and sometimes I ride her in a curb to get her used to it so it's not such a shock firts time in the ring as a "grown up" but personally I think curbs are another cowboy show off!
Now nobody jump on me yet, I'm American I can say that!
Seriously though... western shows and rodeos all stem from cowboys wanting to show off their best horses talents...saddles designed just to work in got fancier and fancier to decorate these awesome horses and be admired... and then bits... now I have a hand made and hand engraved sterling silver E Garcia blued steel curb that I hope will be my mares show bit... it is stunning. And I think, the spanish came along with their ornate metal work and it just became another status symbol...
The true bridle horse used to be the epitome of training, before anybody bothered to do it another way, I think in todays world if you can do it without a bit, thats awesome, but don't feel second class if you have a bit, and unfortunately if you show, you have to follow the rules.
If you ride with compassion and care, theres no reason your bit couldn't just hang there for the show... a testament to your training if your horse will go with or with out a bit! Many top trainers show in curbs as they have to but will use bosals and snaffles at home to keep the horse light and responsive.
As with so much in the horse world, the equipment is only as cruel as the hands holding it. Try not to let bit rules put you off showing, you'll be missing out on lots of fun and a bunch of great new friends.