What's to stop players suiting up in Combat Armour whenever they venture off ship?
Your Captain smacking common sense into you?
What's to stop real life people from suiting up in scuba gear with a fire fighters outfit over the top whenever they leave the house? You know, just in case of a tsunami or fire.
Less drastic: What's to stop you from slinging a 40 lb backpack full of spare water, rations, medical supplies and survival gear whenever you venture from home?
What's to stop someone from wearing white after Labor Day?
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As with most things, there is no single simple answer and often it's a combination of things both pro and con that need to be weighed.
I'm shifting this back to weapons for discussion because some may think my example of going around in scuba and fire gear silly although personally I'd think someone in public with combat garb a bit silly too.
In many places in the US it is legal to carry a weapon as long as it is not concealed. I live in such a state but rarely do I see people slinging guns. Why is this?
In this case, not because the law level prohibits it.
Perhaps it draws too much unwanted attention from law officials.
Perhaps it draws too much attention from criminals.
Even though it's legal, businesses have the right to refuse service and ask you to leave.
It's uncomfortable.
Not at war and violent crime is rare, especially during normal business hours.
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Other considerations could be the availability of the equipment. If it is only available to those in the military or law enforcement then while the item itself may not be illegal, if you are not currently in the military then perhaps it's assumed you obtained it illegally. Perhaps you are a black market weapons dealer. We have these nice bracelets for you and we'll be searching your ship now.