When a member of our family becomes sick, we don't ask everyone to vote on possible treatments? We go to doctors who are trained to diagnose the cause of sickness and offer appropriate treatment.
When a scientist publishes a new study, we don't ask everyone what they think about the study? We ask other accomplished scientists to do a peer-review and offer their opinion on the study.
No matter what field we look at, we do not rely on laymen to decide the outcome but we rely on qualified experts and professionals.
But in case of establishing a government, which can have a long term impact on millions of livelihood, we ask just about anyone to offer their opinion in the form a vote. Why is this a reasonable system?