Some people are into quantifying and counting and really want to know how many stones they pass each flush and like to track their progress.
Others are just happy knowing they're getting stuff out and aren't interested in mucking about in the details as long as they're on the right track.
Funny how we always seem to marry the opposite type and drive each other crazy. My husband would not only use a colander, he would have a spreadsheet listing the number, size and grade of each stone. I'm more of a Flush and Go type.