The fippable mattresses are getting harder to find. They are still out there but you have to look for them. I carry a few in my store.
So whats the deal?....
My opinion is the industry thinks that if you flip your mattress it will make the system worse. They found that if one side has a small body impression on one side of say 1/2" an inch then you turn the mattress over and get another body impression of another 1/2" inch, well thats 1" now.
I do carry them in my store in the less expensive options. Come check them out.