If someone could make a case for using them, I'd be willing to try them, but to me they are vestigial.
I use them for a few things, but hiking is not necessarily one of them.
Downwind in big breeze and especially in waves, I'll tuck my foot under the aft-most strap to help keep me from sliding forward if the boat decelerates suddenly.
When roll-tacking, I'll use the strap on the opposite side as a hand-hold to help pull me out of the low corner near the end of the tack.
I use the strap as a foot-hold to help get me pushed up to the rail and out on the trapeze.
And, in moderate conditions with the crew on the wire, if we get hit with a gust that I know won't require me to go completely out on the wire, I'll hike.
They're nice to have instead of a slick expanse of trampoline with nothing but the lacings to grab onto.