On an electric car that yells at you your range left and that you won't make it to your destination unless you charge, if you turn on the seat warmers, that range goes down so you have to think about if you'd rather have a toasty butt and have to stop and charge, or just be colder and get there sooner. But you have to charge anyway.
In an ICE powered car, running the heater doesn't have the same effect on range. Because an ICE is hot due to how it works, sending hot air to the car's interior is basically free because the heater uses waste heat from the engine.