I think its cause they are both such icons in rock history.
They both have amazing lyrical talent.
They both have amazing insturmental talent.(although I think Zeppelin is better on that one.... John Bonham the greatest drummer ever by far, Jimmy Page one of the greatest guitarists ever, John Paul Joans a very acceptional bassist and great on keyboards, Robert Plant has more energy and stage presence than most frontmen.)
I could also go on and on about Floyd though.

It's also cause there're are very few bands that are in that leuge of talent and music.
There are no bands like Pink Floyd, Led Zeppelin, and few others, today.
Im not sure if there will ever be any bands like them again.
All the amazing music is not being created anymore.
It's all in the past.
Think about it.

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