why a stronger bit for the horse?

Because way too few equestrians have learned how to properly release pressure when needed. They just keep ripping on their horse's face, offering the horse no release or outlet until the horse isn't sensitive to it anymore. Then, they decide immediately that it's the horse's fault, not theirs, and that they need to get longer shanks or a higher port or some weird contraption that puts pressure on the horse's entire face.

If people would just take the time to 1) wean themselves off their hands and 2) spend a day practicing the traditional "add pressure then immediately release after a response" method, most would find that they could do anything in a mild bit.

In my opinion that's pretty sad.

People should only be looking into greater forms of control at the recommendation of a respected professional who has gotten to know the horse. A harsher bit is not the smart route. With it comes a whole new level of sensitivity for the horse, and while some riders see it as an easy fix, it is not a long term one and will only create new problems.

If the horse has a hard mouth, this is all that will work, is to start from scratch, Or use a tie down, I use flash and figure 8 nosebands, but you have to understand, the horses can open the mouth 2 fingers worth if put on properly, I have a mare who can not use a tom thumb without a noseband, she will get the shanks in her mouth use her teeth to break the reins and bolt when with beginner riders. You have to think if the animal has a safety problem, if not, then there is no use..

no idea, i have truthfully used a tie down for a while on my arab, only bc he kept smacking me in the face with the back of his head, but in that case the tie down worked and once he found out he couldnt get his head all the way up, problem solved. i think harsh bits are just a waste, and yes in the long run they do cause more harm than good, the horse will eventualy start acting worse bc it will sart asociating the bit with pain. we use hackamores, and the youngest has a soft training bit, no problems here,....

It is quite clear to me that those people have not read Xenophon's "On Horsemanship." So much was fully understood about equine training 2500 years ago that it seems a shame the ancient wisdom is ignored today. The work is short, and several English translations from the 19th century are available on line for free. Xenophon is straightforward and easy to understand, particularly for one who already knows horses. Even though he writes to us from a time before horseshoes, saddles and stirrups, many of his methods for thinking about training are genuinely appropriate for today's rider.

Because they are idiots who are clueless when it comes to horses. They are lazy and are looking for a quick fix and they are seriously lacking in ability when it comes to working with horses. Pretty simple actually.

To gain control?