Like today's jam bands (e.g., Phish, String Cheese Incident, Widespread Panic), the Dead did not get a lot of air time, but that wasn't indicative of their popularity with a strong following of very loyal fans. Their songs didn't lend themselves to AM (back in the 60's and 70's) or even most FM stations (then and now). But live, . . . WOW!

A couple of exceptions were songs from
Workingman's Dead and
American Beauty that were relatively short and would fit time slot requirements of radio back then.
My first introduction to the Dead was
Uncle John's Band followed by
Casey Jones. Then came
Sugar Magnolia,
Truckin' and
Friend of the Devil. I met my first Dead Head on the first day of law school in the fall of 1971. Kurt had dozens and dozens of reel to reel tapes of the Dead and we would spend lots of time at his apartment listening to the Dead. Once you saw them live and took in the experience of a Grateful Dead concert, you were hooked. Their live shows always beat the heck out of their studio albums and live versions of studio album songs were always better than the album version.
Last summer I took the Flower Power Walking Tour of Haight Ashbury. Everyone in our group wanted their picture taken in front of the Grateful Dead house.

Our tour guide told us that happens with every group and it is and has been the most popular site in Haight Ashbury. Studio album sales and air time are not the only guage of popularity.