It is obvious that Luggages are fairly common in the Agatean Empire, yet in The Light Fantastic Twoflower explains that he got his Luggage from one of those mysterious magic shops. Terry says:
“That was a long time ago… think of how it’s all progressed. They’ve got real clocks in Ankh-Morpork now, people wear spectacles… you might as well say home computers were rare and special things in 1980 so how come there were so many of them in 1990? What makes the Luggage special is its peculiarly endearing character…”