Because I am true to my demographic, I watch a lot of HGTV. This is maybe a little weird, because I hate virtually everything that the decorators do on HGTV. If these shows are to be believed, our era will be defined by a style I have dubbed Contemporary Bland + Orange Pillows.
Professional Grade is an odd term - I've heard the term commercial grade used more. A commercial grade stove has burners and an oven that put out a lot more heat/btus than a normal stove.
On a fairly high end GE model I saw recently, it can come with one burner that can produce 17,000 BTUs on "power boil" -and the others do varying amount less. My low end oven can do at max 12,500 BTUs. A Garland heavy duty range (commercial grade) has burners that can produce 30,000 to 35,000 BTUs. They can also come with charbroilers that produce 90,000 BTUs. These type of appliances need a special wider gas line to work. They are more powerful than anything a typical consumer (except my mother) needs. They're like Clydesdales.
Commercial grade appliances also got popular because you could beat the shit out of them and they'd continue to work. Also, as a status symbol, they signify that a) you were a serious cook, and b) you didn't just go to Circuit city to get your appliances. You were not hoi polloi with one of them. Then rich people starting liking the look, and the commercial companies started making retail versions that were more expensive than the commercial grade, not quite as durable, but a lot more user friendly, prettier and didn't require you to structurally reinforce the floor. And now everyone wants stainless steel.
In other words, stainless steel has become a status good. That's why all those young couples on house hunting shows adamantly shake their heads when they walk into an otherwise charming fixer-upper and say "No way. I want stainless."