Yea I get that but that's why it's important not to exasperate it by House Rules that allow things like layering Armor, stacking Armor and Cover, and ignoring or hand waving Encumbrance.
That not really the issue though...
GM: "You guys find a tracker vest in the closet."
Player: "Cool. My scoundrel would look fly in a vest. He puts it on."
GM: "Um, you can't. You are already wearing heavy clothing."
Player: " itsjustavest... "
GM: "Sorry, no house rules."
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Player: "Does the merchant have any personal deflector shield generators for sale?"
GM: "Sure. If you can afford to pay the exorbitant price."
Player: "Totally. I've been saving up for months! I buy one. And put it on."
GM: "Um, you can't. You are already wearing a tracking vest."
Player: " itsafrickinforcefield... "
GM: "Sorry, no house rules."
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Where do the rules start? Where common sense ends?