Heat is lazy by nature and doesn’t flow through a house from a single point well at all. People try to move heat via ducts from overheated areas to colder areas but it works poorly.
When you move hot air down a duct, it loses temperature quickly and creates noise. These ducts are often in the ceiling and delivering heat from a vent high in the ceiling does not heat the room well. Ducted heat pumps also deliver heat from this high up position but fail to warm the lower parts of the room. Compared with nothing, its fantastic...
But far better to spread small amounts of heat around a home via a warm water radiator system or an underfloor system.
The heat is delivered in the right place in the room and is easily moved via water in pipework because water moves heat energy more than four times better than air does. The pipes are tiny compared with large air ducts making retrofitting possible and easily fitting in with new house designs.