There's no question that you can make a good living learning to program dinosaur machines in COBOL, but then you would have to spend your life programming in CO

There's no question that you can make a good living learning to program dinosaur machines in COBOL, but then you would have to spend your life programming in COBOL. Good coders want to use the best tools, because using good tools are part of being a good programmer. Unless things have changed radically, those tools don't exist on mainframes -- or at least, what most people consider the best tools don't. Taking one of these jobs is more or less the exact opposite of starting your own company.