Actually it can be arguable that people are familiar with how they seem to work, rather than how they actually do. The myth of bullets punching through armor and obsoleting armored warfare is one(for one, kelvar is basically modern leather armor, and it works just fine against small-arms).
Complexity of crafts presents a further step. Many modern technologies are in their basic form, not that hard to make. Steam engines were around since Ancient Greece, and so were incendiaries, while explosives were discovered before the Dark Ages. The problem was that it takes someone to make the connection between two seemingly unrelated pieces of knowledge, apply them together and you get a new piece of technology. Practicality doesn't seem to come into the picture, you just need the right kind of nutter and the application to bring it to at least artisan-knowledge(because mass production and standardization hadn't been invented yet).
The translation of damage over to game equivalents is another, since realistic armor tends to be more damage mitigation and critical prevention than outright deflection(again, save for small arms, which can be mitigated to zero). Bombs and grenades likewise, we consider them insta-kill or highly damaging(and indeed they are, to most people, who're made of meat). However, in game, characters have enough health to survive brief immersion in lava, which is arguably even more debilitating. Contrasting yield against objects would do better.
