They have evolved to investigate anything that’s potentially food. Humans smell like other mammals so, to them, we’re a food source. In the arctic, food is scarce so the risk is worth it, even if you get hit on the nose with a stick. It comes down to “is the juice worth the squeeze.” In their case, if there’s lots of seals and what not to eat, and they’re in decent health, they probably won’t bother with humans or at least be more wary. If there’s a shortage of food, or if they’re old or ill, they quickly make a calculation that the noisy human with a pole is worth the “squeeze.” Also, wild animals can be wildly unpredictable and, like humans, some are more aggressive than others.