I've never felt the need for straps, and don't use them. [on GG LT+ model]
When on flat ground, if I'm really bearing down on strapped poles, then I basically end up pushing myself too fast. I end up walking at something like 5-7mph, which is just too quick to sustain comfortably. On flat ground, the light touch of strapless is all I need, just to add a little extra kick.
On the uphill, I'll need to bear down a bit more. Straps may come in handy on tremendously sustained climbs, but this is occasional.
On the downhill, I'm typically palming the top of pole, sending the force as directly through the shaft as possible. Also lets my wrist flatten and relax a bit.
For emergency balancing, I'm typically doing a reflex squeeze anyway, and a couple times I've been glad not to have anything around my palm.
I usually don't notice any hand fatigue until late in the day, say 15-20 miles in. It's just another part of your body to condition, I've never noticed any soreness to linger into the next day.
I also like that I can move my hands around the poles freely. I can switch positions, hold the grips "backwards" or "sideways" or whatever suits my interest.