Say, that at your first game as a member, you win luckily to an opponent of a high rating. Then your rating will be *very* high. I've seen people with a rating of 1800, after that it will (slowly) decrease to its true level.
Hence - the highest ever rating can't be of any value if you don't know what happened the first (some fifty?) games until it has settled.
Golden King User 285560
is an extreme example of what I mean.