[lrvick]

Graphics cards and ASICs are high up front cost and ongoing electricity cost that forces them to geographical areas with cheap electricity. Disk based systems are still up front cost, but substantially less cost to operate. Chia style nodes could be very low compute/electricity overhead and could potentially run off raspberry Pis on solar or using spare storage on mobile devices that are already powered on for other uses.

[Nursie]

Yes, but such a system would incentivise the mass acquisition of storage media, pumping up prices, increasong production and having huge environmental consequences.

Proof of storage is just another ecological disaster in the making and I sincerely hope it never takes off.