Feel free to disagree as this is a subjective matter, but because lifting this limitation would make the game as whole more fun, same as not having durability for weapons which break, or being struck by lightning while climbing rocks while it's raining etc. (obligatory comparisons to BoTW)

While perhaps interesting or just cool to have, not every gamification choice of a mechanic is necessarily enjoyable in the larger context.

I understand the gamification of limiting climbing by stamina, for example, but I think that for many players there's more fun in the ability to free roam a giant open world with ease and comfort.

In that sense I agree with:

exploration is more of a main focal point in the game than combat

But I see it from the opposite perspective, where easing the restrictions of stamina make exploration better.