What makes you think CryEngine can't run on older hardware? As a demo, they're naturally showing the engine at its best.
Games "last" quite a long time, too—by catering first to the high-end and then downsampling to be able to run on older hardware you make things "future-proof". When you release your game on iOS in a decade, it'll still look great :-)
Its not very cost effective to create content at a quality that only a small number of users are going to be able to see.