I think the smart bike and rower are very different in terms of what you'd do with them. In contrast to a smart bike a rower who constantly adjusts is much harder to use. In fact on low resistance rowers are almost impossible to use. It's also much easier than on the bike to row at a specific wattage without ever adjusting the resistance (mind you that requires some technique).
I don't understand why pelotons are popular when a tacx/wahoo/etc are lightyears ahead in feel and blunting the peaks of "pain" from beginner mistakes. The more advanced ERGs that adjust are super forgiving and the same would be for rowing, avoiding pulling too much lbf and having your arms hurt for weeks = avoiding the workouts.
People doing HIIT cardio usually blow up if they put out 10% more wattage for a minute or two than their FTP. If a machine makes it so you can workout "forever" and simplifies the interface of games/workouts so users only need to focus on a single metric for game while adjusting all the others, it would be a killer feature.
In particular they don't really look for the same things that someone who buys a smartbike is looking for. Also I would add that in terms of build quality, spinning bikes are much better IMO than tacx or wahoo.
A bit of a tangent, but it's a shame that Kettler bikes never became popular, their hardware is top-notch (proper cycling bar, campagnolo ergopower grips), but they never implemented ANT or bluetoothsmart so were not compatible with Zwift and instead tried to push their own platform.