The very purpose of love on earth is the realization of that heavenly commitment. It may have been solemnized in the heaven but it is meant for earth and the meaning is to be fulfilled here only. With a perfect and eternal realization, you can actually feel the heavenly experience here on earth only and need not have to think beyond the earthly boundary.
Also, it is an interpretation of things or words. One can interpret it like that the marriage vows should be respected and enjoyed with your partner for life thinking that it is solemnized in the heaven and has god's will attached to it. This way people may respect more to their vows better and always try to keep it intact.