I paint almost exclusively on wood panels and not on canvas...but when I do paint on canvas, I like to make my own.
I just like to know what my ground is made of - from the wood structure to the gesso. I want to know that the wood is quality, the linen is quality, and the ground is quality and applied in sufficient quantity.
I think there are probably some commercially made canvases that would come close to fitting that description, but I would still likely add a coat or two of my own gesso to them just to be sure.
My two cents...