Because ideas that don't add value should not be pursued, else you are wasting resources.
Imagine how dysfunctional the world would be if you could never loose money investing in something.
Imagine how dysfunctional the world would be if you could never loose money investing in something.
This brings up questions like "where did that extra $50 come from", but maybe you get the point of the original comment now.
This is the underlying principle of investment, that the money is being utilized by someone for potential economic gain.
If that money is just parked such that its always available for a return then it isn't really an investment.