It is a general airline pricing policy that airlines making more expensive for their local (hub) clients than for clients only transiting through their hub
That is to attract clients to their 1-stop flights rathe than those clients taking a nonstop to/from their local-airline hub For example it is cheaper to fly AF from other European airports than form CDG
Of course, ME airlines entertain a lot of pax with no interest in stopping over in their hub (DOH), except for a short touristic stop. Hence, the country (Qatar) might ask QR to introduce some good fare to allow a touristic stopover, say up to 2 days. One needs to segregate business pax based in DOH and taking advantage of such attractive fares Quite a few business pax would have several intertwined tickets if stopovers were not penalized