We keep things out from the lower tiers, such as Wobbuffet, Kyogre, and Deoxys-E because they would overcentralize what could be an otherwise fluid, flexible, and varied metagame. If these things were not banned, creative, unorthodox, and game-changing strategies and ways of play would be stifled and stopped before they could even begin, and we would become bored.
First of all, we don't ban Pokemon because of "overcentralization" (that most taboo of all Smogon words!). A metagame can become centralized and stale just as easily by banning good Pokemon as by allowing them (see: old UU). We ban Pokemon for being much too powerful for their metagame. Also, as you noted this is presently only true of Standard and UU. Ubers is completely different, not because no one cares but because
it is intentionally different. To be honest, Ubers is a poorly named metagame. It should probably be called "Universal" or "Anything Goes" or perhaps even "Pure Pokemon".
They've done some truly silly things before, just to humor us, such as testing Deoxys-E in the OU meta.
This is a definite excursis, because it isn't really relevant to the rest of the topic, but testing Deoxys-e wasn't all that silly. More than a few people (including me) didn't really think it was broken during its first test.
Due to the fact that there is such a limited pool of Pokemon and users in the Uber tier, the overcentralization and exploitation of the establishment only serves as a cycle and means that the meta will reach equilibrium faster. Because of the fact that we are human, and cannot assess which combinations have clear-cut absolute advantages over others with relative ease, some may argue that this is a non-issue. I disagree, however, because we have seen things come to a standstill too fast before. Not one that's been 100%, and that may very well be impossible, but ones that have come dangerously close.
If I understand you correctly, you are concerned that Ubers could centralize to the point where it becomes essentially a game of rock-paper-scissors. But to be honest, no Pokemon metagame has ever come close to that. There have always been some players that have consistently won far more than others, and that would not be the case in an essentially non-competitive metagame.
As you look at the Uber tier, don't tell me you don't care about how it's balanced. If it really was just a banlist, you wouldn't apply standard clauses such as Sleep and Double Team and the like because you really wouldn't care about how it would turn out. But this is untrue, people do care. If you canceled standard competitive rules, people would object from the time the idea was conceived. The only reason why you don't have an active movement to change things is because our minds, as humans, do not clearly and sufficiently see the mess the Uber tier is right from the get-go, and thus play in it under the impression that it has some sort of balance.
Sleep and evasion clauses are not a matter of competitive balance, they are a matter of style of gameplay. To be honest, you could *probably* have a balanced metagame in Standard without sleep clause, and you certainly could in Ubers. However, it would be something of a pain having a sleep absorber on every team, and at any rate the game is much less messy without Double Team/Minimize (and without Sand Veil and Snow Cloak, but we can argue that some other time....). Centralization is a poor measure of "messiness" for a metagame, and particularly for Ubers. Ubers is as fun as it is not in spite of its centralization, but because of its centralization.
As a final note, when it comes to Ubers, I am always in favor of banning less. I don't see the standard clauses so much as bans so much as the general conditions of what it means to play Pokemon competitively, but if I had to choose one way or the other, I would remove the sleep and evasion clauses before I would ban any Pokemon from Ubers. To be honest, I would not want to ban even Jibaku's theoretical super-Pokemon.
Finally, this topic does not really belong in Stark, since it is really a classic example of a thread that belongs in Policy Review. If you really want to see this idea fly, I suggest you find someone with PR access that is willing to endorse the idea.
Edit: Noted, for future reference.
