Problems sourcing the battery I believe, either became unavailable or uneconomic, I forget which. Part of it might also be that - dare I say - people tend to like passive Precisions, certainly by comparison with P/Js and J/Js, be it cultural or technical, just seems to be the way it is (compare the number of active Jazzes on the market with active Precisions for example). The shame is that the P-Retro was an engineering masterpiece, beautifully designed and engineered, and given most people don't want to have either modify their bass or remove the whole Precision pickguard, John really did his homework. Beautiful piece of kit, sounds beautiful also.
I disagree with some of the comments re pickups above, yes they make a difference but whatever that difference, an active circuit will allow you to fine tune it to perfection. I guess it all comes down to what sound is in your head when you're making the choice. I had a passive bass with two Sims/Enfield Quads, PUPs that can do pretty much anything that can be done with various combinations of 8 traditionally oriented coils, and while the range was impressive, adding a J-Retro really gave it life and added some character that, while it wasn't missing, was less obvious and harder to find when run passive.
But all of this comes down to preferences and experience really 👍
I've recently picked up a P-Retro from here that I'm hoping to run in one of my Enfield Quad basses simply because I really like the way it works, much more like a Wal preamp than a more traditional B/M/T boost/cut model. Wonder if I can add Wal to the hard-baked Precision/Jazz/Ray settings of the Enfield 🤔