The biggest advantage of radiators in our daily lives is safety of heating.
Without radiators the only ways to keep warm are to wear many a layer of clothes or to burn a fire.
Now burning a fire in the home can be nice in a fireplace; but a fire in every room?
Maybe a fire in your bedroom when you sleep?
I don't think so.
Hot water flowing is safety in the house and warmth.
Radiators are also more important to keep engine and motors cool. You will find they work exactly like heating radiators but with colder water inside! Every car has one; as do most means of transport!!