Well I think this a very broad generalization that is for the most part not true as it reflects a lot of myth about steel bike frames. While a well made carbon frame will likely have improved power transfer properties over comparable steel frame, those differences on paper are for the most part not noticeable to the average rider, particularly since we are talking about high end steel frames like the Riv, that use light, thin tubes, which in the hands of an expert builder can be built into very stiff and efficient frames. Moreover, many of these are designed with long distance touring and riding in mind so will deliver a more comfortable ride than will a race-minded set up of a lot of carbon frames, mitigating what is a relatively small energy advantage of the carbon. So a rider who struggles over hills for 100 miles on his high end steel bike this year, then drops 3k on a carbon bike in hopes of finishing stronger but does nothing to improve conditioning, may find himself regretting the expense when he still feels like crap at the end of the century next year. IMHO, for the average consumer who just likes to ride his bike 50-100 miles a week with the occasional century, steel is still the best bang for the buck for combination of performance and ride. Which is not to say I would drop 2k on stainless since what I am after can be had at a much lower price point. This is also not to say quality carbon doesn't have advantages over steel when it comes to power transfer , but these generally show up in more aggressive circumstances like racing and fast club rides.
It isn't just about power transfer. Frame material and most importantly differential section modulus of carbon frames...a concept certainly RJM would never understand because it is well above his pay grade
allow a frame builder to create a greater difference between vertical compliancy and lateral stiffness all while producing a much lighter frame. A stiffer front triangle in torsion produces a bike that handles better. Again, if speed isn't a priority, it doesn't matter. I have owned 30 steel road bikes...likely many more than the responders to this thread. I get the allure. To me carbon is far superior if performance is the objective having owned many of each.
For touring when carrying a 70 lb payload plus rider, it really doesn't matter does it. Steel makes sense...especially if designed for a 300# plus payload.