You will get most rewards at the end of a quest line, not when finishing 1 quest within it. May this is the reason?
EDIT: some quests have multiple objectives (am I using this term right??ó_Ò') and there are no rewards beside the small kickback for leveling up a building to a specific level for the first time.
Questlines have multiple quests with one or multiple objectives within it. You will get your reward items when finishing a questline.
sry man my englisch is bad and since April 1st I am more backed than a forgotten lasanga...holy duck my LASANGA!!!!!1!11