I wash because I want to use pure material, not something soaked with unknown 'stuff'.
I literally take a micrometer with me to Wal-Mart when searching for a new patch cloth. I look for material that seems like it would make good patching, check to see it is pure cotton, then measure. Ladies give me funny looks when I do the micrometer thing :blah: , especially when I also pick out some baby blanket flannel to make into cleaning patches. :wink: