Why do some admissions processes request an exhaustive list of jobs held? This question is motivated by Should you list irrelevant work experience on graduate school applications?

In that question, the OP cited text from one graduate school's question about employment history:

"[List] employment experience (including part-time) since secondary school"


Why on earth would a graduate school admissions committee care whether a candidate worked part-time in a dry cleaning store from May to August of 2003?

Are they just trying to narrow the field by making the application process more tedious and daunting?
My suspicion would be that the school with such a requirement has a very narrow age window it desires in its graduate students, or at minimum desires that the ink still be wet on their baccalaureate diplomas -- the "train them up young" approach. Listing all post-high-school jobs is not usually terribly onerous for the typical 23-year-old.

I can't speak to how appropriate this is across disciplines. I can only say that where I am we only ask for a résumé and do not specify how far into the past it need go, because we value learners of all ages.