According to Led Zeppelin's management company Q Prime Management, the band isn't comfortable granting rhythm game developers access to its catalog of master tapes, which are necessary to create authentic Zeppelin-performed game tracks.
Harmonix and Neversoft have previously made use of cover bands to bring popular songs to the Guitar Hero and Rock Band franchises in the absence of master tracks. Amidst a sharp spike in sales and broad popularity, follow ups Rock Band 2 and Guitar Hero World Tour will be comprised solely of master track versions of songs.
Led Zeppelin is often cited as one of the most requested bands for rhythm titles. Reports recently surfaced that the Beatles' management team was in talks to bring the celebrated pop rockers' catalog to Rock Band and Guitar Hero, though no official announcements have yet been made.