So I think you're much too eager to dismiss the value of stationary bikes.
I definitely agree with their characterization of these infomercials.
While I think OP is misdirected, I knew all sorts of people when I lived in the suburbs who had exercise equipment they bought for the idea yet it was left unused year round. And the idea of taking a walk outside through the clear air of suburban Texas seemed lost on most of my neighbors who, of those I knew personally, did not have the excuses we like to make up for them in these threads.
Though I'm not so sure guilting them in these threads is the most effective way to change behavior -- we probably both agree there.
Assuming the point is exercise, of course. Bike commuting and utilitary cycling in hilly areas can be more of a challenge, but I'm assuming that if we are comparing to stationary bikes, commuting isn't the point.
You could get a trainer--a device that allows using a regular bike indoors, which takes up less space and only needs to come out when you don't feel like going outside.