It's also a problem if you're an artist that makes something 'close enough' to Mickey Mouse, and you don't have the resources to both fight the legal battle, and support yourself while your income stream is shut off due to the legal battle.

It's also a problem if you'd like to preserve old art or repurpose it for the modern era. The tragedy isn't Mickey cartoons, it's all the less-famous art that is being lost forever with the passage of time. Which could have been reissued by whoever came across it, were it not for perpetual copyrights making that impossible to do legally.