Why wouldn’t we? We would be able to double spend and get the exchanges to hold the bags.
We would also be able to be buy back on different exchange and potentially be able to get new UTXOs that that are spendable on both chains and loop.
If exchanges don’t have replay protection in place (mixing dust from spam chain after the soft fork) then they are vulnerable.
If they add replay protection they have to pick a side, if they choose spam then they have wipe out risk which can stay dormant for weeks, months, years , or decades.
