Because it was primarily made to be seen on the internet and on streaming apps. Stuff like Bluray and DVD is a thing of the past for children cartoons, specially one that can be streamed at maximum quality for free on youtube.
There is a English release of series one on DVD in Australia but as @BigRed said home media is dying which is a shame,
Yep it dying is a shame considering we still need rid 2001, beast wars 2 and neo, rescue bots, rescue bots academy, and the rest of rid 2015 on dvd.
Because these days people would rather netflix , amazon and disney dictate when they can watch something .... and live in empty houses with everything they " own " floating around in cyberspace , telling google what adverts to send in their direction .