My father got malaria in North Africa during WWII. I remember he had a relapse and was really sick for well over a week. I mean really, really sick. This is a man who never missed a day of work for more than 45 years (other than the malaria).

People have different levels of risk tolerance. For me, YMMV, I find that taking the pills is less of a hassle than the risk of contracting a disease that will follow me the rest of my life.