I'm totally fine without an SP/XP reward from the sidequest itself as long as:

1) The enemies grant me normal SP/XP. Really, if I have to go kill them, they should give me normal mob rewards. Even if they're a bit lower level, and as such give less SP/XP than I'd get from killing things on my level.

2) I get something *useful* from the quest. This can take the form of unique or useful items, good snippets of story, or progression towards unlocks (see: airships, chocobos, abilities, zones, etc). In an ideal world, the last two would be guaranteed and the first would happen occasionally throughout the quest chains.