The most obvious answer is that most of us don't realize the state of enlightenment is either possible or desirable. You may believe it requires a level of heroism and sacrifice that is beyond you, that it's reserved for people, who, like the Buddha, renounce everything, who leave job, home, and family to spend years practicing fearsome austerities, meditating for long hours, cutting themselves off from ordinary life.
This all-or-nothing notion of enlightenment is deeply rooted, and insidious. I often get questions from students who experience an expansion of consciousness and then worry, "But if I keep doing this, will I have to give up my family? Will I lose my personality?" If we think pursuing high states of consciousness means giving up other aspects of life, it won't seem like an attractive option. On the flip side, we may be attracted to the idea of enlightenment yet imagine it to be a way of bypassing ordinary challenges and irritations, and then we may get discouraged if we don't experience an immediate transformation, or get frustrated when we aren't lifted miraculously beyond the everyday demands of work and family relationships.
