Im not sure why Pistons are disabled but it would be great if it was enabled it could add a whole new level to ECC and it has lots of use so please take in my suggestion
Not just that (well that isn't the reason at all) but because of the plethora of piston-related dupe bugs as well as the fact that they not only cause tons of lag but can also completely crash the server. So, no.
We once had Pistons, they where disabled due to dupe issues, and that Dupe issue still wonders the land too this day. Sorry, maby in the future, but now? No.
We had a piston contest for one day while the real map and server were updating to 1.7, other wise we've never had pistons.