I've never understood stationary bikes. If I want that kind of exercise, I'll just get on my bike and ride it...
Depends on where you live. If you live in an area of the country where you can ride year round, then yeah, I don't understand stationary bikes either. However, if you live in an area where there is snow and bad weather quite a bit of the time, then yeah, I understand stationary bikes. Sorry, but you can't ride a road bike in snow and slush, as not only is it dangerous, but you have to fight against all the snow on the ground. Me? During the last 8 years I was in the Navy, I got rid of my car and rode a bicycle everywhere I went. When I moved from Florida to Newport RI, I got a mountain bike for whenever there was snow, so that I could still ride into work. But, I still rode a stationary bike on occasion whenever I wanted a good workout.
When I moved to Amarillo, I foolishly sold my mountain bike (thinking I wouldn't need it anymore as there isn't much snow in Amarillo), but found out later that they could get pretty good snow accumulation on occasion. I still ride my Lemond Zurich when the weather is decent, but have actually considered getting a stationary bike or a wind trainer for when the weather made it difficult to ride a road bike.