There are some non-financial arguments for continuing the proof-of-work chain as “ETH PoW” (or whatever they ultimately decide to call it, because “ETH PoW” frankly stinks). Above all, rational or not, there will be some uncertainty about the stability of the new Ethereum chain after the Merge. If something goes truly catastrophically bad with the Merge, there is some chance users, apps and even assets (see below) will migrate back to the PoW chain. In this scenario, positions on the “old” chain could act as something akin to insurance.
