'pure-finders'

I read this quote, describing the squalid nature of Georgian London -

"At the lower end were occupations now not only lost but barely recorded: that of the 'Pure-finders,' for instance, old women who collected dog-turds which they sold to tanneries for a few pence a bucket (the excrement was used as a siccative in dressing fine bookbinding leather)."
The Fatal Shore, by Robert Hughes

- and immediately behind my eyelids appeared images of the old asian women who wandered around the Berkeley campus, who reached into the trashcans and stomped the plastic bottles and aluminum cans flat as students like me walked importantly from point A to point B, glancing briefly at them as long as it was certain that eye-contact would be avoided.

And I wonder what their stories were that I never bothered to ask, and never bothered to record, and whether they will be lost as well.