Im not opposed to direct measures. You could do observational studies looking at how frequently people litter when nobody is watching or surveys of how bad people feel littering is.
This would help you get a pulse of the comparative culture. That said, observing culture directly IS measurable.
You look at culture that leaves trash everywhere and that itself is a data point.
Sure, and you can also ask why drawing conclusions from the ether is superior to relying on examining actually measurable parameters.