Why Is the Risk of “Forks” a Consideration in Physically-Settled Crypto Futures?
A blockchain "fork" creates a new version of the cryptocurrency. For a physically-settled contract, the clearinghouse would need a clear, pre-defined policy on which version of the asset (the original or the new forked coin) is the deliverable asset.
This creates logistical and financial uncertainty. Cash settlement avoids this by simply referencing the price of the original, dominant chain's asset.