Rope abrasion is a real problem, even with conventional ropes. It is even more significant with smaller diameters. I have seen an 11mm rope lose about one-third of its diameter from abrasion on sandstone as the result of just one relatively jerky rappel. Fortunately it did not snap.

If I take a rope on an outdoors trip, "just in case," it is just as likely to be used for leading or belaying, applications for which I would only want to employ a "real" climbing rope.