Most of the Naval ships, in High Guard, especially capital ships dont have ANY Low Berths, they have Barracks.
Its the cheapest most desperate means of travel, thats it. There is a massive risk the rules state that. Dont want the risk, dont use Low Berth. It is meant to be a drastic option, not a regular travelling option. Thats the point of the black humour, Captains Lottery. Would it be open to abuse. Yes. So are the other methods of passage.
If you dont think its "realistic" dont use it. There is plenty about the RPG that isnt "realistic".
The Traveller RPG isnt just the Imperium even if you use that setting. But the Imperium isnt as written one big safe setting, quite the opposite. It has roving Companies of Mercenaries, Pirates, hijackings...ships that arnt maintained, the risk of Misjump....