genuine question, because I forgot a $20 with the laundry at work and I don’t know if the laundry is going to look green or if I’m going to get a white $20 back and clean clothes…
I think the washing resistance is more so to prevent counterfeiting in which people bleach bills and print them to be higher denominations.
It functions that way as well, but durability for every day use is also a consideration in the material choice. Bills being uncounterfeitable isn’t particularly useful if they’re constantly being removed from circulation because someone left a bill in their jeans when they washed them.