Everyday life is full of strangeness. Why do you drive on a parkway and park on a driveway? Why does the 24-hour convenience store have a lock on the door? Why does the refrigerator have a light and not the freezer?
Well, at least for the last question, there might be an answer. Today I Found Out talked with Ed Dougherty, a refrigerator technician. He says:
It all comes down to cost/benefit and features. While it’s not terribly expensive to add a light, sealed fixture, switch, wiring, etc. relative to the cost of the whole unit, it does cost something and manufacturers want to save every dollar they can in the cost of manufacturing their product. Studies have shown that people don’t open the freezer nearly as much as they open the refrigerator and certainly not as much for “browsing”. Ice-cream sandwiches and similar items aside, when people open the freezer, they are generally going to be looking at getting something out that takes some further preparation. So the kitchen light will probably be on anyways. Thus, the benefit of having a light in the freezer is much less than in a refrigerator that often gets raided at night, to the point that manufacturers would rather save themselves the money of putting one in, as most people don’t really care or notice whether their freezer has a light or not.
But this isn’t the only plausible explanation, says Today I Found Out.
With non-automatic defrosting freezers, particularly with older, low-end models, there is the problem of ice crystal build up from the humidity of the air introduced when opening the freezer. This not only reduces the efficiency of the freezer itself, but also would reduce the utility of the light or even obscure it altogether, making it pointless (and hence the benefit vs. cost plummets even further).
Other possible explanations include: freezers are too packed for a light to be useful, old style lightbulbs would shatter in the cold, and lightbulb would heat up the food too much.
More at Smithsonian.com