I think the bulky bit is just to impress the male body type -- for the longest time, fantasy warrioress were bikini-clad amazons, they are lucky to get pauldrons, let's the cultural imprints are still there -- inverse triangle upper torso simply looks more impressive. Part of that might have also been the pop-culture fantasy of the American cartoons in the 80s. So the thought process was likely muscle-bound Heman/Conan/what-have-yous gonna wear armour? Bigger torso! Giant pauldrons!I have never understood the real reason why (especially in fantasy) armour must look most times clumsy, albeit '''magnificently decorated'' (sometimes). Perhaps had first something to do with sportsfellows like american footballer or (ice) hockey players, both looking more like Hulks. Similar to weapons, a sword or axe looking like 50 pounds in weight is not really combat-ready. Perhaps i was even in past to old as those fantasy startedbut for M&B it is something 'new'. (shall fit to console?)^^
Take Warhammer, for example, their normie humans wore mostly normal armour, though yes, the higher-ups are quite decorated. But the northern barbarian baddies wore armours with pauldrons, when modelled-as-depicted and used in the Warsword Conquest mod, blocks the vision in first person view -- though this also has to do with how games render first person views is different from how we'd see from two eyes.

The one on the left is a normal dude with rich parents and maybe trained alot. The one on the right does 1,000 push-ups every day since birth, in the winter, outside in the snow, and has supernatural strength granted to them by otherworldly dieties.