Some corporations made hefty investments in big iron. That doesn't make them economically viable today. I still believe that performance, energy conservation, space utilization, HVAC optimization, etc., etc. are reasons for updating to the latest hardware and the operating systems that they run. From a strictly hardware standpoint, the old stuff gets hairy to manage and maintain.

You can keep driving that 1979 AMC Matador, and you can keep rebuilding the engine, and patching the rust holes. But after you've spent thousands on the upkeep, you could have bought a new car that gets better gas mileage and won't strand you on the freeway half-way to work on a rainy morning. Any corporation that didn't look to the future, is the corporation where you'll find the dinosaurs. And that doesn't say much for corporations like State Farm.