Don't look now, but age, gender and ethnicity often do indicate income levels of adult-human-consumers in America. The fact that they still exist and live long and consume media and music is enough to want to attract them. They certainly have more income and leisure time than 20-somethings, GenX, GenY, and GenZ-ers who are struggling under the crushing economic conditions of incomes not Hikeeping pace with cost of living, or the younger ones not suffering through graduating during or after the recession of 2009-10, or even now not being able to get a job out of college and still living with said Baby Boomers (or GenXers, for that matter).
As for the poster who alluded to Baby Boomers having enough money to pay for subscription services rather than listening to the radio with ads...neither they, nor the rest of us, would have to seek out subscription services (or podcasts) if radio properly served audiences anymore. Those of us who are veterans are well aware that various permutations of 18-54 are the target demos. But, hello--perhaps radio needs to also target -64 and -74 demos in order to keep them.