Well if you don't mind me being direct the first thing I would say is that yes, it is very much your fault for letting them get that way!
It's not as if the tyres are hidden, do you never check them? Whenever you look at the car from the front you can see plenty of the front tyres, sidewalls and all so no excuses there....
However, whether it's your fault that the tyres have worn this way, may not necessarily be your fault as it sounds to me like you either have some serious alignment or tracking problems which you need to get sorted soon or the same will happen to the new tyres.
It may be worth having a word with the supplying dealer to see if they will investigate under warranty, if they're good they might do this for you but in reality it's the sort of thing that can happen really easily banging a kerb or similar so they'll probably say you'll have to pay for it.
Good luck.