Why not to use Crystal instead of PHP?

Flat-file instead of database is great idea! Then why not to use something like Crystal language instead of PHP? We would surprise everyone by running a simple box, lets say 256 mb (or maybe 128) ram 1 core server, it would work as fast as a PHP app on 4 GB 2 core server. I would love to see Grav stop using PHP & switch to this approach. Crystal looks more than ready for such flat-file web back end & blazing fast (Dont even compare native code to PHP) and probably more readable than PHP .
http://www.stefanwille.com/2015/05/redis-clients-crystal-vs-ruby-vs-c-vs-go/
https://github.com/kostya/benchmarks

Grav is open source so feel free to port Grav to Crystal or whatever you like.