I don't think anyone has ever said that the home cook must use stainless steel. In the kitchens I have worked in we have used everything from the aluminum pans to copper clad. It really depends on a number of factors.
Cost- you mention that they are cheaper. This is as true for the restaurant as well as the the home cook.
Conduction- The burners on a professional range give off a more even heat. On most home ranges you will have drastic hot spots without something more solid to disperse the heat. This is why All-clad and their ilk sandwich the stainless around an aluminum core. Aluminum pans heat up quickly, a very important thing in a fast paced kitchen.
Skill - There is a lot to be said for being able to cook using a raw aluminum pan and not end up with half of your dinner stuck to the bottom. I'm not saying that the average home cook cannot do this, but I can't remember the last time I was cooking omelets at home and didn't use a high-quality non-stick pan.
Ease of cleaning - The harsh chemicals used in kitchens aren't really friendly to most finishes. So, why waste the money on a pan that is going to be replaced frequently.
FYI- These are my opinions based on my experience in the kitchen both at home and professionally.
Flip
"Beer is proof God loves us, and wants us to be Happy"
-Ben Franklin-