A couple of reasons come to mind. First and foremost, the wedge line is for wedge play where bounce and grind are primary considerations in their design. That changes the more you go to longer full shots. Also, the wedge line is a subset of the Titleist club line and building and marketing full sets of Vokeys would create an internal competitive market that neither Titleist nor Bob want to do. You can get the performance and feel characteristics you are looking for by playing the 620MB's. That's how many pros and better amateurs like to put together their sets. I think we can all agree, the Vokey's are great!

I assume the obvious reason is vokey is a wedge magician

Just my opinion as I wonder what he would gain making full sets of irons

Like a putter, a wedge is a specialized more individualized club. His wedges are very fine tuned and he is a master at his skill. I think the current line up of Titleist clubs, Vokey Wedges and Scotty Cameron putters works very well for consumers and pros. When I order my Titleist irons, I order Vokey chrome wedges so they match. =)