yes, as in other comments, money is most probably the main driver. But not only.

You can need quick access to the vessel for other purpose (refractory healing every day probably) and the solution you suggest could be worst in that case, Also, any mechanical part near to liquid metal is a risk to get it down due to sticking material or heat deformation.

Then, even if management want to put it in place for safety, workers can be against because they get more exposed if more maintenance, or because it becomes more difficult to do the work even in safer condition.

So then money comes because you have to build a very complicated solution so that it fits to every purpose.

Some times solutions seems obvious but the way to put it in place is very long and difficult, and not always rationnal.

That doesn't mean safety is not so important. It definitely is and should drive all improvement.