Let's be honest, storytelling is one of the weaker points in Bethesda games, Elder Scrolls and Fallout. In particular, the minor quests essentially only provide the bare minimum of plausible excuses for the PC to get involved, and are often simply glorified dungeon treks with a nice mace or suit of armour as reward at the end from the quest-giver. Even the main quests often have stunningly implausible scenarios, for instance in Oblivion where the escaped convict hands over the amulet of Kings to a monk he has never met before, who openly says he is sceptical about the player's intentions, but who then simply says "As unlikely as your story sounds, I believe you", with out any detailed fleshing out of how the player character convinces him, and promptly sends the PC off to Kvatch to find the one remaining ray of hope for the Empire, even though this man is clearly a convict and quite possibly a murderer, thief, rapist etc. etc.
But the thing about Beth's games is that the gameplay is usually so good that it's possible to ignore these glaring issues and just glory in the sheer joys of a dungeon trek, and think up your own reasons and rationlisations. However, this is clearly an areas Bethesda could improve. Fallout 3 had some good ideas. There should be more options in coversation, more ways of convincing people. Falliut 3 did that very well indeed with mutiple quest paths in many quests, some hidden depending on your character's attributes and skills. This should be carried over to other games. Hopefuly there will be more of this in Skyrim although the removal of attributes makes any bullying based on Strength or cajoling based on Charisma impossible. However hopefully there will at least be multiple ways of completing quests.