I want to start this out first by saying one thing.
bsms - You said you are a backyard rider, but that isn't true. You are a HORSEMAN. I wish more people who were at the higher levels would think like you. You might not think it but there is something about you that always seems in tune with your horse - Trainers could learn a thing or two about that.
Anywho, the problem is that there isn't a lot of common sense in the human race and ignorance rampant. Like Tiny said, people can only make decisions based on what their experience has been.
I used to be on the whole "Only bump up to a curb after you have a finished horse". Let me be the first to call BS. If only it were that simple. There are MANY bits between the snaffle you start your colt in, and the bridle you finish your horse out in. If you aren't showing, by all means, go in whatever you want - But the horseman of the world developed these bits to be used and show their horsemanship. It takes a HORSEMAN to bump a horse up into a bridle. A backyard rider would screw it up, yes, and that is probably why people say never to step up until your horse is finished.
Then we have to debate what
finished is. My mare is up in the bridle, she has competed and been hauled a lot, is BROKE as you can imagine. She stops, spins, changes leads, lopes pretty, solid loose rein transitions. Been on trails, runs barrels, packs kids, carries flags, been roped off of and gathered cattle. She has won money in both the reining pen and the barrel racing arena.
I do not consider her finished.
Is this a shock to anyone? Let me explain my reasoning. This mare is a great mare and I trust her with my life. HOWEVER, she is NOT a bridle horse. She is not a solidly winning barrel horse. She is not a put your hand down and work cutting horse. She's simply a broke horse who is being seasoned and happened upon a couple checks and awards.
I have started a lot of colts. I realize more this year about how incorrectly I had been doing it. I now have colts who are miles more broke than most you see at local level shows...In fifteen rides.
Sounds ridiculous right? How is that even possible?
I saw an opportunity to learn from a great horseman and I took it. If I hadn't of done that, I'd still be taking a year to accomplish what I can now do in 90 days.
I am not a great horsewoman; I am still very much so a student, and that in itself is amazing to me. I always help anyone who needs it. I always try to be humble, even when it's hard. I still giggle and grin like a kid when I do something right. I still ask for help. I still get stuck and have to take a step back. I still get confused or frustrated or annoyed where I have no right to be. This is all a part of learning.
Poor horsemanship is everywhere. It doesn't take a genius to ride a broke horse, and anyone can get on a colt and buck it out and get them to steer left and right, or spur it to run. It takes a horseman to teach a horseman, and it takes the mind of a horseman to retain that knowledge. Only though horsemanship can you really achieve that finesse, and willingness out of your partner. You have to know what tack to use that will enhance your success, but you have to know it isn't magic. You have to know all the little things as well as the big things.
A bad horseman could ruin a horse with the best fitting saddle and kindest bit in the world, but a good horseman could make a good horse out of the cheapest tack and worst backyard breeding in the world. It's just when you get that magic combination - The great horse, the perfect fitting tack, the right weight in your reins and use of your aids....And the great horseman. That's what makes the difference between the millions of good riders and the great ones.