People contribute because everyone needs to belong.  Perhaps in many, their lives are lonely and bleak.  This allows them to anonymously put forth ideas which plague them and get various responses, some of which might be their own opinion.  But, if someone is cruel enough to tell a question asker that the question is foolish, the asker has the satisfaction of knowing that they will never have to meet that person; perhaps unlike their real existence where they might be unmercifully scorned or ridiculed.  The internet is a SAFE haven for many people who wish to BELONG.