Ask and ye shall receive
It's not just focus groups, sending documents out for review is just as bad.
Possibly the worst aspect of "processes" in business is the number of people who wish to review, approve or be FYI'd on documents that are, essentially, none of their dam' business. Mostly it's just to pad out their days (shades of: "why don't estate agents look out the window in the morning? Then they'd have nothing to do in the afternoon") with the illusion of activity.
However, once these people get a copy of a document, they feel the need to suggest changes - whether they know anything about the subject or not. One boss I had made it his policy to require at least one change to every circuit diagram he reviewed - just to show that he'd examined it. This was a long, long time before Dilbert and PHBs. After all these induhviduals have suggested their changes (none of which are returned until the deadline), there then follows a period of argumentation regarding why you chose to ignore their "input" and the inevitable politicking if you happened to point out an error in one of their documents - expect the favour to be returned in spades.
I now adopt a policy of NOT circulating proposals, papers or designs whenever possible and everyone seems happier for it (though not as busy as they'd like to appear). I reckon focus groups act the same way - if they always said "yup, that's fine" there would be a feeling that their time had been wasted - that they hadn't exercised their "right" to an opinion. Maybe the secret is in the questions they are asked. If instead of open-ended critiques, focus groups or approvers were asked specific, if diversionary, questions about particular aspects: do you prefer X or Y? then it would be easier to obsfucate the responses and come up with exactly what you intended to in the first place.
After all: you can't please everyone, so you've got to please yourself.