I have a thin leather strap that I put through the d rings of the saddle leaving a big loop that I hold as if it's another rein. It has held me on during some sideways spooks!
Yes, yes, very much yes! Mine has saved me countless times. I rave about it to any and all my horsey friends if they're having confidence issues and /or have a sharp or spooky horse. It's there whenever I need it, even if just to tuck a couple of fingers round if I'm feeling nervous but also has kept me literally anchored in the saddle when horse has full on bronked. One of the best bits of horsey kit I've ever bought.
I use an R-stor for hacking. You could make a DIY one yourself far cheaper. I do like it though, it gives a bit of security if you have a spooky. I never remember to grab neck straps!
My dressage trainer has a grab strap on every saddle, competes at a high level with one so I started doing the same. Haven't really needed it but it's reassuring it's there if I need it. If I'm riding anything young or jumping I'll add a neck strap as well, means I always have something within easy reach.
I have one because E can forget which order his feet go in downhill. I hold the handle so I don't accidentally sock him in the mouth if he trips and his head goes forward.
It's absolutely essential for dismounting a Suffolk. It's a long way to drop so holding the handle means I don't have to take that extra step back on landing (reins wouldn't reach)
I find that anchor straps and neck straps are in the wrong place for my hands , but breast plate is perfect - I needed breast plate with last saddle but not with current one but keep using it anyway as it’s very handy when hacking out as pony is a bit spoooky.
Well my strap saved me today when a pheasant flew out of the hedge and my 4 yr old took off ! Without the strap I would have come off backwards as it took both of us by surprise!