The amount of research funding is finite. Why spend it on something highly speculative when there are many other things it could be spent on which are not speculative?
It's finite but not explicitly conserved: science funding is around 1% of the US national budget and can change (a bit).
In practice you're right, though, usually new funding in one place gets taken from somewhere else. But if the world really wanted scientific progress we could afford to fund some more speculative projects.
