...is that there would be a way to have the players want to run around in light armor, instead of the heaviest plate they can find. Yes, I know there are creative ways I can do this (excess heat, armor prices, etc), but they feel forced. And my friends would have immediately caught on to what I was doing and would get grumpy.
With the rules as written, it's really hard to get someone to have a "hoplite" style character with helm, shield, and spear, and maybe leg greaves. It's too bad. But I guess that's what Runequest is for. :)