What Is the Main Disadvantage of Physically-Settled Futures for a Purely Financial Speculator?

The main disadvantage is the logistical burden and cost associated with the physical delivery process. A purely financial speculator is only interested in profiting from price movements and has no desire to take possession of the underlying asset.

If they forget to offset their position, they face the hassle of arranging delivery or acceptance, along with associated costs like storage, transportation, or network fees, which reduces their overall profit.