I think what we are talking about here is somewhat of a chimera, in more than one way.
My old Kleins had some carbon composite in them, as my DBR WCF do.
This gives you a combination of characteristics that perhaps are more than the sum of their parts.
Even when we are talking about Al full sussers, other metal is also used in parts integral to the frame, without which it would not be a frame, in the same way tent poles themselves usually do not make a tent frame without their end pieces.
Carbon fibre itself is of course not used in isolation even to make carbon frame components, it is not really a frame material in the same sense as the others being considered.
In fact the truth is that most frames are actually some form of composite.
The response you will keep hearing is that steel is heavy.
Well, it does not need to be. However you have to pay somewhat for lighter weight and the extra work that entails for the builder, tube maker.
A high end steel frame can weigh most of a kilo more than the carbon frame you might pay half the price for.
If you buy new...
But you can get a sub 2kg steel frame for buttons (<£50) and build up a 24/25lbs steel steed that you could ride around the world quite happily, not quite sure I would feel that way about any other material.
My old Marin Sausalito was one such bike. Bought it from a bike messenger and then thrashed it over tens of thousands of miles with panniers and it never skipped a beat.
I wouldn't do the same with a carbon or Al bike.
Nor Ti, although I can understand those who would in the same way some guys go round the world with motorbikes they could not get repaired locally anywhere.