Many winter hiking boots are short for several reasons. First, a shorter shaft height allows for better flexibility and freedom of movement. Additionally, the lightweight design enables easier mobility during outdoor activities. Despite their shorter height, these boots provide adequate protection and warmth without added bulk, making them ideal for day hikes and winter conditions. (Important note: winter conditions on the milder side, not arctic conditions or extreme cold).
That said, there are winter hiking boots that go higher up the leg to keep mud, water, and snow from getting inside. Taller boots are better designed for hiking trails with less difficult terrain.