They are easy to maneuver once you learn how to fly. People just need to take the time to read and understand the manual -- and, spend the time learning how to fly safely. When those steps are skipped, a crash is inevitable.
They are easy to fly and therefore you become comfortable too quick which leads you to become complacent or take further risks. In other words - cockiness.
Another reason is spacial (sp?) awareness. Standing at the wrong place can lead to misjudging depth/distances. Eg flying between a goal post.