Probably because Denmark has excellent cycling infrastructure and didn't allow an automobile-centric culture to shift the responsibility of driving safely onto vulnerable road users.
Because this Playmobil bike helmet is only a prototype and not for sale.
http://metro.co.uk/2016/10/03/someone-made-a-lego-hair-bike-helmet-and-everyone-thinks-its-awesome-6168247/
Odd English, I would say "Why do you ride your bike" or "why do you cycle", but never "Why do you bike".
fordi det er ikke sejt!