Why do probabilists have a preoccupation with urns? Why is there an off-putting amount of questions from probability or combinatorics that involve an urn? Is there some historical reason? Did someone not have a box, or other container, on hand and had to bother their grandparent's remains to help solve a mathematical puzzle? Or did some author decide that one only draws balls from urns, and future authors kept repeating the same scenario ? It has always just struck me as weird and thought maybe someone here knew.

questions with balls and urns are members of a class of problems that became known as Urn problems, see: < which quotes Jacob Bernoulli himself and explains why he used the Latin word urna, also the present day Italian word for ballot box.