Our oldest horse, a senior citizen, when we bought him, I was told he'd been ridden for years in a mechanical hackamore and that's what he likes, and he's just no good in bits. Well, he's okay in bits, if you have good hands,and I just don't like mechanical hackamores.
I've tried doing groundwork to "soften him" on the bit, and learn to yield, but he will stubbornly lean into it and sort of go into a lala land. Or he works himself into a lather, and he's old so I feel sorry for him. So, I gave up. I ordered a mechanical hackamore or "hackamore bit" for him. I'm not too sure on the adjustment for these things, so tips are welcome, but so far so good! He's been so much BETTER than he ever has for us. It's like there was an audible "ahhh" of relief. So, while I still maintain they aren't my cuppa tea, he's happy, husband is really happy, and I guess I am, too.
I reckon I'm just saying that just because you have preconceived notions about a piece of tack, you shouldn't knock it until you try it. I'm not a huge fan of these things,I won't be using them or suggesting them for everyone, I prefer my snaffle bit.However, in this instance, it's worth it's weight in gold.
*side note, the horse while due for dental exam soon, has been cleared previously for having dental issue to cause issues with a bit. He just is not forgiving of beginners (my husband) with rein pressure. Seems kinda mean to force it on him, and nose pressure seems to be less traumatic.
And what's my gripe about them? They have the same potential for harm as any device and seem like a crutch or excuse to not learn how to use your hands better, because there's the excuse that it won't damage the mouth, but they are nose crunchers, IMO. But as stated, they have a purpose. I still expect hubby to work on how he uses his hands ....and I don't feel the horse really has a problem with the bit and his training overall, but there are some holes in his training. He doesn't tuck his nose, but he will back up. Little things like that, but for a horse that's expected to walk around the pasture once a week, he's fine in a m. Hack.