Yup. Poor heat in the winter is usually a stuck thermostat, but depending on miles and of course care taken to follow the recommended schedule of the car other things can start to go. Hoses for one thing needs to be check along with belts unfortunately the hoses for the heater core aren't check often.

Hoses are made of rubber and will deteriorate over time just like tires, belts and any anything else made of rubber. They start to lose their oils and get brittle over time. This is why if you store your car for long periods of time you should drive it once in awhile (recommend once a month) to get the rubber in the tires (and hoses) somewhat pliable again.

But if you are not getting heat most people say thermostat cause it's the easier fix and most common. If you have a cracked hose or heater core it will drip or leak warm coolant which goes through the core to heat the cabin. The heat will escape through the crack and hence less heat in the cabin