Why we keep commandments?

From here:

Professor Isaiah Leibowitz was opposed in principle to trying to explain the reasons for the commandments. In his opinion, one should not seek such explanations, since the commandments were not intended to answer our needs, be they psychological or educational, nor to provide us a mystical experience or the ability to influence higher spheres. For him, the purpose of all sacrifice, like all the other commandments concerning the relationship of human beings to G-d, is service of the Lord for its own sake alone, as opposed to worship which is not for its own sake, but to answer our own needs. As for the details of sacrificial worship, Leibowitz repeats Maimonides' explanation, holding that they are arbitrary and devoid of specific significance.

Or, as the Maimonides said it himself  "He does not change, for there is nothing that can cause Him to change;" therefore prayer, sacrifice and the performance of other mitzvos must be of no use to Him. They can't change Him, or cause Him to do anything, nor can He be said to desire us to perform them because desire suggests some need that is fulfilled through our actions. Such a need can not be ascribed to God: He can't change, so He can't be fulfilled.

 On Twitter this came up in conversation where @bemaimon made some related points at the expense of @rabbidmk, a man rapidly becoming the Washington Generals of Twitter. Here they are:  

:)

@bemaimon: ..."want" is rank anthropomorphism. Hashem doesn't want, need or desire anything according to Rambam.

@rabbidmk: Then why did He command them?

@benmaimon: Who says there's a reason? Are you assuming God thinks like you? Why do the laws of physics make heat rise? They just do

@rabbidmk: Suggesting there is no reason is tantamount to suggesting G-d does unreasonable things.

@benmaimon: Not unreasonable; just unrelated to reason. Suggesting God must have reason is saying He thinks like you

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