[acdha]

The part of a block depending on the hashes of its ancestors seems very useful for tamper-evidence, which is useful in many applications if you can handle the data model & volume. Being able to definitively say who changed what and when is worth a lot if you have to maintain data which could be used in court and a distributed ledger, Merkle tree, etc. is more predictable and much cheaper to run if you don't have to maintain mining-level infrastructure.