They generally switch the machines from mostly cold drinks in the summer to 20-30% hot drinks in the winter. It's a well known and common way to warm your hands, buy a hot drink from a vending machine.
Quite the opposite: many Japanese work uniforms mandate gloves all year round in roles where we usually wouldn't use them, eg. taxi drivers. But the appeal of a hot drink on a cold day is pretty universal, I certainly appreciated them when I was camping in northern Hokkaido at the tail end of summer.
