A: Cos its the only Beatles album currently available on vinyl, according to this US article.
"... Since the album was released on vinyl in the U.S. in 1991, it has sold 151,000 copies as opposed to 4.1 million CDs for the same time.
Many are curious why the band’s iconic Sgt. Pepper’s Lonely Hearts Club Band isn’t the top dog or perhaps Rubber Soul, maybe Revolver. The answer is easy: the only vinyl Beatle studio album to be released, so far, is Abbey Road.
The day when the entire catalogue is repressed will surely come and, yet again, another surge of record buying will push the band’s total worldwide sales toward the inevitable three billion mark (take that Michael Jackson)...
... A breakdown wasn’t available, but The Beatles have now sold more than 10 million songs and more than 1.8 million albums worldwide on iTunes."
Hat tip to Simon Grigg for the link - Simon mentioned on Twitter that the Beatles catalog is available on vinyl outside the US, see amazon.co.uk.