I have no idea, Tom.
But if I had to guess, many times even those used to a wall-oven will convert to a one-piece std. 30 inch (75 cm) free-standing range to get a bigger oven. It is also less expensive than two separate pieces.
To get a second oven, one can install a micro-convection range-hood over the stove, or get a Maytag Gemini with two ovens, or have an electric couter-top oven and/or rotisserie.
Sears now even sells models whose storage drawer *Triples* as a storage drawer, a warming drawer AND a little oven.