I would imagine the Cobra 29 BT was discontinued because it didn't sell well. It probably didn't sell well because 1, not too many people needed one and 2, the radio overall probably sucked. Just a guess.
I don't know if the radio sucked or not, but I recall looking at the radio and briefly considering it.
My thought process went something like this, "Hey, that's a spiffy feature! Cool technology. But... what would I do with it?"
I can already pair my phone, via Bluetooth, to the stereo in my truck. (And I do, usually for listening to Podcasts, Iheartradio, and the occasional phone call that my wife wants to participate in). One or both of my GPS units have Bluetooth, so I can have a speakerphone conversation via those. (Tried it once; found it sucked) Plus, I have an actual Bluetooth headset. It works very well. Having Bluetooth capabilities on a CB is incredibly redundant and pointless, for me.
Now, I suppose, if you weren't much on listening to music or talk radio, it might be interesting to connect the CB to the stereo,via the Bluetooth (assuming that's possible; it probably is), and utilize the sound adjustment features, but I guess the usefulness of that depends on how much conversatin' you think you might be doing.
That was my take on it, anyway. And, I would guess that the target demographic probably felt the same way.