Why you should clean your refrigerator occasionally

Well, more often than I do, any way. Like most modern fridges, mine automatically defrosts itself.

 Here's what happens when you don't clean your fridge very often -
 In the back of the cabinet is a condensor panel that is usually lightly frosted.
Every 6 to 8 hours, this panel is automatically heated for a few minutes, and the moisture falls into a receptor just below.
There's a little drain hole in the middle of the receptor, allowing the water to drain to a pan under the fridge, where it evaporates.

Occasionally (in poorly maintained appliances) stuff sticks to the frostiness, and then falls down and blocks the little drain hole.
This situation is usually indicated by the formation of a puddle under the fridge.
Remediation of the situation involves finding a long thin pointy implement, and poking it down the little hole, followed by mopping out the bottom of the cabinet, and possible the vegetable drawers as well. And the floor.
Truly dedicated housekeepers may even wish to investigate the drain pan, or maybe move the fridge and do a REALLY good job  of it. Not me - a girl's got to draw the line somewhere...