Why hey cortana works only in english? Makes no sense since its only 2 words to activate, they could make it avaible in other countries too. Same algorithm i think, why dont make avaible for other languages?
It's not a very widespread ability since only two phones support it right now and Microsoft has other priorities like Windows 10 and Windows 10 Mobile.
This Having "Hey cortana" will depend on your hardware.. As for the only in English bit.. As she gets optimized for each region they might implement a new or translated voice commands to wake her up.. For now there are keyboard shortcuts
That make it useless imho. If i want to use her, is because i cant use my hands. Using vocal assistent with hands is not for me, i find it useless