If you saved your paper dollars under the mattress, this wouldn't be much different from saving some files on the storage media in your computer. Whether material or immaterial, the form in which value is saved or stored plays no role. What really does is the subjective value people attribute to the things and which you cannot redeem in order to store safely in your home. If security as well as safety are among them, then anything that provides security and safety will have that subjective value (which you just can't squirrel in the backyard because it is purely a mental construct in people's heads)...
So you're actually confusing issues here (I hope unintentionally)
Well, I understand the form in which value is stored is not important: besides paper dollars and metal coins under my mattress, I use credit cards and checks, and I understand my bank keeps dollars in files in their computers. But that's all dollars, legal tender.
So maybe I'm just a confused old guy, perhaps my 50 yo old brain can't catch up with you guys

The notion of legal tender is useful only when you pay your debts to banks or taxes to the state (which are debts too). In many jurisdictions, you can be lawfully refused to do business with and may not insist on striking a deal. This would render legal tender (lol) effective only as an offered payment for debts...