There are a variety of reasons, some being that the horse's mouth is very sensetive to bits, a bit would not improve the horse's preformance, or that the horse was not trained with a bit.
Well, bridles are used for when you are riding. Most have bits, although there is one type called a bosal that uses no bit. Bridles also have reins to hold while riding. You can use a halter like a bridle on a horse, just using the halter and a lead rope, but you cannot attach a bit so it can be very UNSAFE. When riding, you should always use a bridle. Halters are made to lead horses from place to place.
A bosal hackamore may work. There's also a number of good bitless bridles.
It depends what you are using it for. Generally figure-8 bridles are used on eventers, jumpers or equitation horses. It helps keep the horse's jaw closed for more control by the rider. Not all eventers, jumpers or equitation horses need them though--only use a particular piece of tack or bit if you understand what it does and know that your horse needs it.
A dressage bridle is any bridle used during dressage, it's not actually a type of bridle.Most bridles used in dressage are black snaffle bridles with or without a flash attachment. Double bridles which use two bits (A bradoon (or bridoon) snaffle bit and a curb bit, typically a Weymouth are used.) and two reins are employed for a more finished response.Either of these types can employ a flash attachment which is a strap of leather that attaches to the noseband on the top, encircles the mouth and is buckled close under the chin to prevent the horse from evading the bit. If adjusted properly it does not harm the horse, but in the wrong hand a flash attachment can be tightened too much and cause discomfort.
To grate cheese and sad people can eat it slowly bit by bit.
The cost of a bridle can vary. I have a nice one that I bought for $35. They range in price - some can be hundreds of dollars depending on the designer and leather quality. It depends on what you want to spend. I prefer to get a good quality one, which might cost more because it has better leather and will last forever. It depends on what you are using it for, too. If trail riding is your thing than you won't need an expensive one, But if you do showing and or pony club you might as well spend the money.
It is preference of the trainer. D. Wayne Lukas is the trainer who kind of started the white bridle trend. Most of his former assistants such as Todd Pletcher and Steve Assmussen will use white bridles as well.
There are five main categories of bits. These are:SnaffleCurbPelhamGagNoseIn dressage, there are restrictions on the type of bit you can use. Only snaffle bits, and in higher levels, double bridles, may be used and are classed as 'legal'.
Use a 1/4 inch bit, that's only very slightly bigger, less than 0.025 of a mm. larger.
Try a bitless bridle. Many horses hate bits, because bits often hurt the horse. It's really hard to use a bit and NOT hurt the horse with it. Most bridles and bits use pain or the threat of pain to make a horse do something. So, I advise getting a bitless bridle and training him instead of going up a bigger, stronger (and therefore more painful) bit.
use no power
People use fractions when there is slightly more or less than a whole