It's hard to argue with the decision. Groovy Decay (and its demo-heavy doppelganger Groovy Decoy) is probably Hitchcock's least well regarded album. Hitchcock himself has all but disavowed it. Also, including it would have blown any chances that Hitchcock would be declared the godfather of freak-folk.
The truth is there are some very good songs on the album ("52 Stations," "America," "The Cars She Used To Drive"), along with a few clunkers ("Old People Scream," "Midnight Fish"). But the whole album is undeniably weighed down by its slick, "new wave" production aesthetic, and the reliance on horns and synths to carry the melodies rather than guitars. Unlike much of Hitchcock's work, Groovy Decay sounds dated.
Listening to the album I am reminded of the episode of Freaks and Geeks in which Sam is convinced by a clothing store sales clerk at the local mall (brilliantly played by Joel Hodgson) that all his troubles with the ladies will be over if he purchases a snazzy new "Parisian Night Suit" (which is really nothing more than a hideous powder-blue polyester jumpsuit). The results are predictably painful. No one should wear a "Parisian Night Suit," but some people (say, John Travolta) are capable of pulling off the look anyway. But poor Sam can't because the Parisian Night Suit is simply the opposite of who he is.
Groovy Decay is Robyn Hitchcock's Parisian Night Suit moment insofar as he dresses his music up in a style that simple doesn't fit his musical personality. Somebody convinced him that if he only adapted his style to the slick new-wave ethos of the era that he could have a hit. To his eternal regret he followed their advice, and the results, while not exactly cringe-worthy, are at least a little embarrassing in retrospect.
None of this should discourage you from downloading the album. No, it's not Hitchcock's best work. Yes, it sounds more than a little dated. But it is still certainly possible to hear the good songs beneath the production.
A few things got left off the latest digital incarnation of Groovy Decay. The demo version of "Midnight Fish" was originally released on Groovy Decoy, which featured mostly demos recorded in advance of the Groovy Decay sessions. Even the demos, recorded with former Soft Boy Matthew Seligman, are slicker and more produced than anything Hitchcock had recorded up to that point in his career. Special "disco" versions of "Night Ride To Trindad" and "Kingdom Of Love," originally issued in 1982 on a 12" single (a misguided attempt to get played in clubs?) were also omitted from the program. Can the world survive without disco versions of Robyn Hitchcock songs? I suspect so. But you shouldn't have to if you don't want to.
Also, since this album is no longer available in any worlds but the virtual one (or perhaps in some other parallel universe in which people prefer dancing to Robyn Hitchcock over Rihanna and J-Lo) it no longer comes with any tactile artwork. But that is no excuse for the lo-rez image--gleaned no doubt from a quick Google image search--Yep Roc features on their website. Feel free to paste the artwork above into your iTunes library.