Saving on your energy bill?
An absolute temperature of 19°C feels like only 17°C at 10-20% humidity, while it feels like 19°C at 60% humidity.
You can compare this with a sauna session - although this ritual leads you to believe that the temperature in the room is much higher, only the air humidity has risen. Higher air humidity therefore means that you can save on energy costs, while the temperature in the room remains the same (and not unimportantly pleasant).