Once upon a time horsehide was used in the States a lot more than it is now. I have seen muleskin boots that were sixty years old, worn hard and put up wet, and never a crack. The owner claimed they simply would not scuff.
The old time Buster Browns...for those of you old enough to remember...had horsehide toe patches to prevent scuffs. Horse fronts are used regularly for linings in Europe and the US..especially in the Orthopedic Trade. As Bengal Stripe mentioned, it was used extensively for aviator (Bomber) jackets. That alone would suggest a flexibility that belies any worries about cracking. All the horse fronts I have seen were soft and had a reasonably good "hand" (drape). In fact, in my opinion, one of the reasons horse fronts are not used for footwear is that chrome tannages tend to be too
soft and stretchy. The veg tannages I've seen tend to be dense...I like them for welting. I suspect the biggest reason horse and mule (probably indistinguishable for all intents and purposes) fell out of favour is the reverence in which Americans view the horse.
We don't eat horse either despite having been told by greater culinary experts than ourselves how delicious it is.