I might be wrong, but I would guess that compressed air is not so much involved with processing chemicals, or in thermodynamic applications where precise temperature are not important to the downstream process, such as powering drills and tools. Other gases include a wide range of uses, refrigeration being one. As well as some of those other gases may have pronounced heat transfer effects in either high or low direction that could be important to capture.
--Einstein gave the same test to students every year. When asked why he would do something like that, "Because the answers had changed."