Why can we duplicate items ?

[Cockerel]

I don't agree with you mate
If we can't bring more than one royal so how can we get to Odin ?
that will make the game so boring

What you are saying only affects the game's difficulty, something that devs are always juggling with (in each update) ; so as for me, it's not a recevable argument.
The main obstacle is visibly the fact it woud something different... That is quite deplorable, in my opinion. NI is not a role-play where you "unlock" items, enabling you to use them as many times as you want, is it ?