Why do wine cabinets have heating and cooling functions?

Q. I notice some of your wine cabinets have heating as well as cooling functions, why is this? 

A. This is for those customers who wish to keep their cabinet in an unheated room such as a garage or barn.

In the winter the ambient temperature will drop below the set temperature.

In these circumstances, a heater will gently come on to stop the temperature inside the cabinet from dropping below the set temperature.