Let's say the chain is worth $100 unforked and the value of forking is $10. The value might be $105 if the market only thinks forking is 50% likely, and can remain uncertain depending on how much voting information leaks out. If the fork succeeds, value jumps to $110.

I'm not making this up out of whole cloth either, merger arbitrage funds make a living on these price jumps in equities.

As a meta comment, it's probably unwise to make such sweeping negative claims in a field as varied and immature as economics/finance. You'll always find broad exceptions, since the definitions are all made up by humans out of convenience.