My basement is bright and open and literally covered with toys. In the movies, however, the lowest levels are always home to crazed psychopaths, dead bodies and torture chambers; so why do people insist on descending those fateful steps upon hearing a strange noise? Because it's a horror movie, that's why.
Movie characters always seem to make the dumbest decisions possible for our viewing pleasure. Why doesn't anyone look through the peephole before answering the door; think twice before picking up a hitchhiker or install a window covering or two. C'mon, fictional characters (and lazy screenwriters), you know your mamas taught you better than to take candy from strangers!