Good question, and I've never read why.

When I took alpine travel the SOP was an axe that touched the ground/snow surface gripping the head and extending the arm downward. Now SOP seems inches shorter.

One theory is to accommodate carrying it on the uphill side when following a slope. Ascending a steep slope shorter better accommodates plunging it ahead, uphill. Do folks still cut steps with them? That would be easier and it may be that shorter is more effective/less dangerous for self-arrest.

But as a "walking stick" on the level it's worthless.

Hopefully somebody who actually understands will chime in.

Cheers,