One reason: in the lyrics David Bowie is mentioned. (Immediately followed by my all-time favorite group, Steely Dan. See? It's always about me!) For both series and even for 'Ashes To Ashes' (the sequel to the UK's version), Bowie's music has been an inspiration.
The second reason (and my favorite): The lyrics suggest a connection to "The Wizard Of Oz", which played out to the very end of the 1973 sequence (and with the return of Frank Morgan in the 2035 sequence).
"Life is a rock but the radio rolled me
At the end of my rainbow lies a golden oldie"
"Life Is A Rock" is an infectious song and probably impossible to sing along. So here's a YouTube video that helps out with a picture guide......