they do sell ski-specific poles that are adjustable. they are a bit tougher than trekking poles and have different tips and grips. i have adjustable BD poles and they are great because you can also make them super short to stow on your pack if you need your hands free. also the adjust-ability allows you to have longer poles for skinning, or different sized poles for traverses.
as for straps, if your skiing in thick trees and shallow powder where you are close enough to he ground to hit an occasional root or branch, id leave the straps off, or at least VERY loose. my old poles were made by swix, and they had a thumb tab in addition to the straps. when you arent wearing straps, the tabs work like little hangers between your thumb and forefinger, so if you drop a pole it stays in your hand, but if any force is applied to it, like getting snagged on something, the tab will bend back to allow the pole to release.
Leki also makes poles that have a strap which stays on your gloves all the time and they click into the top of the grip, but its held by a spring that will release when enough pressure is applied. thats great because you can always wear your straps without worrying about your arm getting yanked out. the downside to that is that there are more moving parts, which means more opportunity to break.
if your skiing really deep pow, or above timberline, its best to wear the straps all the time because there isnt much risk of them getting snagged and if you loose a pole in deep pow, its gone forever.
