It's probably not a bad idea. Steel is one of the things that an industrialized country needs to produce to protect its own sovereignty. Letting it shut down and just hope you'll always be able to import enough steel from other countries is a bad long-term strategy. You'd be left unable to fend for yourself.
i.e. if you have a lot of financial resources and can buy 1000 ships cheaply for the cost of propping up your steel industry to build 100 ships, should you buy 1000 ships (or the steel needed to build them quickly) to instead?