wow,i love the over thinking of the simple act of draining a cup of fuel,the rag mostly dries out and i throw it away once its fully soiled from say wiping down a filthy drive chain etc.
no #$%*, what did you guys do when you were kids? Around my neck of the woods it went something like this..."Hey lets use this gasoline to make flaming pentagrams in the street again...I don't want to mow the lawn..."
My guess would be that you weren't the one paying for the 30 cent per gallon gas.

As kids in the 50s, we delighted in running repeatedly through the voluminous fog made by roving DDT distributors through the burbs to "control" mosquitoes, even though it "tasted weird" and kinda made your eyes water.
Here in the US, our cars must have an evaporative recovery system for the vapors in the gas tank. Our gas pumps must have special fill nozzles to prevent vapors from entering the atmosphere during refill. And, we have "spare-the-air" days where "the ordinary people" are not allowed to burn wood in the fireplace or use gasoline using machines to trim the yard. (Not to be confused with the "Flex alert" days where we mustn't use electrical appliances or yard trimming equipment.)
I'd hate to think of the additional legislation that would be enacted, if the politicos and evironazis found out we were letting gas soaked rags to simply "dry out". It's just not the "green" thing to, in these days of saving-the-environment-awarene$$.
We're such an advanced and caring society, you know. (sniff, ah the emotional swell has made my eyes all watery.)