Part of the issue with these sorts of console add ons is that they just split the addressable market further. ISV's either have to address only console owners with the add on, or they can address everybody with the console if they can manage without the extra hardware. Commercially, this can be a hard sell, which makes it difficult to sell the add on, making it even more difficult to write software requiring the add on.
You're being too positive. Only two add-ons in the history of console games have been successful: the Famicom Disk System and the PC Engine CD. All other add-ons have failed to sell enough to warrant vibrant development. Note that both add-ons were japanese successes.
No add-on has been able to survive more than one year outside Japan. Not even PS VR, whose sales are too low.
Despite its success, it still had a lower attach rate than the Famicom Disk System. In terms of software, after the first year no one could make any good money selling Kinect titles.
> Kinect for Xbox 360 continued its momentum in 2011 reaching 10 million Kinect sensors sold worldwide to date. Not only were sensor sales an overwhelming success, but Kinect drove significant game sales with more than 10 million standalone Kinect games sold worldwide to date
From 2011. At any rate, it obviously satisfies the grandparent’s comment on success. (Also, you may be thinking of the Xbox One, which they received flak for bundling with a Kinect)
Microsoft knew add-ons simply do not work long-term. That's why they put a Kinect in every Xbox One's box. Didn't solve the problem of everybody was over with the concept though.
The Genesis had a peripheral like this in the Sega CD; it didn't sell well— mid gen console hardware changes of any kind are risky, but none more so than changing the distribution medium, where you risk bifurcating the audience and alienating those who only have the base system.
I really loved my Sega CD though. Shining Force CD and Corpse Killer (a FMV shooter) seemed revolutionary at the time.
I also had some turn based Dracula adventure game where you chose how to spend your time that was terrifying to me so I once hit the “rest” button in my Victorian era London apartment until it was 1994, which I thought was pretty hilarious ( Dracula would just immediately kill you when you ventured outside but 10 year old me didn’t quite realize how video games worked).
The PS1 didn’t really have those weird experimental FMV games but wow demo disks were my bread and butter for a poor kid.
I had tried the Sega CD, model 2 I think that attached on the side instead of under. They always failed and we ended up returning them. I don't think it was the optical parts if I remember right, something about a poor connection between the two hardware devices.
Sega 32X worked at least, sadly it wasn't very popular either.
If I recall correctly, one of the first iterations of the prototype Playstation was exactly this. The original Playstation started as a collaboration between Nintendo and Sony.
There was the Famicom disk-system released in Japan which (I assume) used the lower port: https://en.wikipedia.org/wiki/Famicom_Disk_System - although that was based on floppy disks rather than CDs.
Not to be to nerdy about it but Famicom is the NES, not the SNES. The only thing released that used the bottom slot on the SNES is a Japan only satellite modem.
