Skiers thumb is usually caused by improper use of ski poke straps. Any high speed falls that I’ve had the wrist was the least worry for injury, I would consider the spine protectors way more important.
Now if snowboarding, a wrist injury is extremely common, simple because of how you catch yourself in simple falls.
You can still get minor sprains with no straps just because a life-long skier instinctively grips your poles if you're going to crash (so you don't have to go back to pick them up), ask me how i know.
Agree it is less important than spine (which is required for a lot of camps/teams) as that prevents a serious injury; but your thumb is still going to be a very common but non-serious injury.
It maybe possible to retrain one self to learn to just ditch your poles and get hands arms safe when crashing, but I don't know exactly how to do it; as I'm also a gripper. In comparison, my friend who came from snowboarding is instinctual a ditcher cause he learned falling on snow with hands free and open.
I don't think you need to get thumb or wrist protection if you are healthy; but if your thumb or wrist is already sprained , get thumb or wrist splints at least to wear while sleeping to speed up your recovery.
If you feel you may injure your thumb or wrist to the degree that you're looking for protection; ditch the poles and ski with no poles.
For snowboarders there is all kinds of protection and different levels, but for wristguards in particular I have dakine wristguards which is more of a soft-protector and not hard plastic to just take most of the impact; as I'm still a complete snowboarding noob. One of the instructors I was learning from ,had snowboarding mitts with built-in protectors as well which looked pretty cool. Definitely easier to use with loose mitts with long loose gauntlet cuffs, versus with 5-fingered gloves or short cuff.