I think the biggest issue is that shipbuilding sucks as a business. Unless you are a large company with many shipyards, you are producing a small number of ship

I think the biggest issue is that shipbuilding sucks as a business. Unless you are a large company with many shipyards, you are producing a small number of ships every year, and the ships take a long time to build. Any particular shipyard will likely have gaps between orders due to a number of essentially random factors. If you can't transfer the workers to other shipyards, you have to lay them off. And then you may have hard time getting new orders or hiring the people back once you have work for them. If you are from a country with some shipbuilding, you've probably seen the same news cycle repeat from decade to decade. A shipyard gets a big lucrative order. It delivers a fancy new ship. This repeats for a while. Then the shipyard is in financial trouble, as there are no new orders. People get laid off, but the shipyard goes bankrupt anyway. And then some foreign company buys it, and the cycle starts again.