If aluminium radiators are so much more conductive and efficient than steel radiators why do we not all change to such radiators which will save fuel

[arabbadot]

Aluminium radiators are used for het pumps as they can reach higher temperatures more quickly. Due to the fairly constant low heat provided by het pumps the rads stay relatively hot . Why not change steel rads in boiler heating systems and use less fuel by reaching the required temp. Much quicker.
Puzzled.

[Mosaic]

Because the world price of aluminium is at a record high, and doing this would make your house a tasty target for itinerant folk whose cultural traditions include the theft of metal.
And the labour costs involved to take out the existing and replace with newly-purchased...
And the very un-green suggestion that new rads should be bought for the sake of new rads when old rads are working fine.....