Combining two paid itineraries
I get that UA won't let you combine two saver award tickets into one itinerary that uses less award miles than the single itinerary. What I don't get is why United won't let you combine two paid itineraries into one. For example, United is happy to fly you from LAX to MGA for about $600 in E in mid-June and happy to fly you from LAS to LAX for between $49 and $89 in mid-June in E but trying to book LAS-MGA produces ridiculous fares. Why?