Because I'm a selfish greedy river rat bum. All seriousness aside, walleye just taste better than any other fish and many fisherman pursue them. So since it is a fragile and limited resource (they aren't very successful at spawning) if fisherman got good at catching them, the population would suffer considerably. With today's technology fisherman are getting better and better at locating and catching walleye, that many quality fisheries are ruined by over-fishing. Believe me when I say that a lake can not be big enough to avoid this. If walleye were like crappie or white bass and their spawn was just as successful, I wouldn't care as much. Call me narrow-minded or selfish, but yea, that's my view anyways.
On another note, I'm all about helping people catch every other fish, just not walleye.