Psychic cues are subtle, it's easy for your own thoughts, fears and desires to overpower them. Winning the lottery is a life changing event, so it's next to impossible to view it dispassionately. It's much easier to pick up on what happened to some random stranger's missing pet or something else which doesn't affect you personally. The other problem is you would have to choose a series of numbers, and numbers are notoriously difficult to perceive under any circumstances.
Valid point...I guess for the same reason that healers don't live forever.