I think it is related to the 'pub-crawl' where people visit as many pubs or bars as possible within a designated time, stopping to have several drinks at each place. A sketch crawl works much the same way, with sketches 'collected' along the way. So, whenever I can, I map out a route through my neighbourhood or someone else's (when I am traveling) and have my own sketch-crawl; recording vignettes of life there.
Each sketch usually takes 10-15 minutes, to capture the main forms and some details to be finished afterwards.
* though this year I resolved to finish my sketches 'on-site'.