I think the multi cam unit that needs professional (enthusiast) installation will never sell big in a mass market retailer type environment,
And yet I know a lot of people who have installed dual cams like the F70 or reversing cams, reversing sensors etc. and they aren't particularly 'hands on'. There is a huge market for car accessories where installation isn't as simple as sticking something to a windscreen & plugging into the power socket.
In fact, even around the home there is a huge market for DiY installations of things like CCTV, burglar alarms etc etc.
And these people aren't tech savvy or big DiYers - My 84y/o dad, for example, bought himself a set of reversing sensors. Sticking the sensors on his back bumper, running the cables into the boot (behind the number plate), scotchlocking the power cable to the reverse light wire then running a cable through the car to the small display stuck to the front of the dash.
This is the same guy who tried to drill a hole to put up a picture and ended up creating something you could shove your thumb into!
I also note that there are a lot of people out there who are happy to pay someone to install a bulb or a wiper - I'm guessing they would be more than happy to pay extra to have someone install a multi-channel camera system in a car.
I also believe one of the problems in the market is the price point. My price range has been a maximum of about $150. I have noticed on car forums that people are looking for less since money is tight for quite a few people (and hence how I know so many people with the F70!), so these people are looking at the G1W up to the Mobius or maybe the mini 0801.
You also have to bear in mind that tech is racing along - so why would anyone wish to spend big bucks on a camera that might be out dated in 6 months' time?