The playable character and what motivates him is a unique and ever-present issue for RPG development. You can make him a part of your universe, giving him friends, memories, a family and while it can help solve the problem of motivation it surely violates the agency of the player; indeed, it voids all later development of that character. Equally so, the tabula rasa playable character makes the player wonder, "Why am I doing this again?" What is your approach to this problem?

Well, it takes two to tango. The player is expected to buy into the story and go along with it. The developer is expected to respect the player and spare him the pain of "You are an emo kid with an attitude who won't rest until his beloved kingdom of Animia is freed from some emo evil".

I think that Fallout nailed it perfectly. Your character draws the short straw and is sent to look for a water chip in the wasteland. That setup covers different motivations, interests, and reasons. You may want to find a water chip because you want to get back to the safety of the vault. Or maybe you are glad to get out of the claustrophobic vault and want to explore the new world and see what it has to offer.

AoD's main quest revolves around locating an ancient temple. Obviously if the player says the he/she doesn't care about some temple and would like to settle down and open a bakery instead, then there is nothing we can do to help. Providing artificial motivations like "you father, whom you love oh so dearly, went to look for this temple and you won't rest until you find your dad" is kinda lame, so we help the player to find an object (a map) that will sooner or later lead him/her to one of the three different parties that are interested in that temple for very different reasons. Counting your character's natural curiosity (we do our best to interest the player (and thus the character) in the temple), that's 4 different reasons to get involved in the story.