Another reason to actually give rewards for offline play, is that the antagonists can be given a group of raiders that don't even total to a third of their level, giving them close to free run of the mission. But the no rewards for solo missions give the players kind of a crappy choice, wait a long time to get into a mission to have your ass handed to you by a 5-times your level antagonist, or play missions for low gold rewards and no progression given for time put in. Honestly, that will lead people to not play the game again.