While I can imagine the paper US dollar to serve as input for toilet paper, it is beyong my imagination what input can be digital money (botg cryptocurrencies and digital fiat).
I can't speak for painlord, but I think he means by commodity "asset", that is "object to which property can be assigned". It doesn't need to be a material object, it can be a conceptual object too.
A commodity usually implies some materialisation. But this is nitpicking.
Why does one desire to have property of an asset ? Why is one ready to provide effort, to provide other assets in order to acquire property of the desired asset ?
There are 3 motivations:
1) the asset is a consumption good (education, joy, entertainment, food, objects to show off with...)
2) the asset is a capital good (with which it is possible to produce other assets)
3) it is speculated that the asset will be tradable for other assets
Of course, 2) and 3) are "indirect" desires in order to provide more with 1) in the future. The desire for them is simply part of a plan.
Asset is the object of property, and one of the characteristics of property is the right or the power of denial of access to others.