The phrase is connected to Talmudic incidents in which the Sages said this phrase after failing in attempts to replace the people who baked the Showbread and the people who compounded the incense in the days of the Temple of Jerusalem. It reflects both grace to accept what one cannot change and recognition that everyone has unique and irreplaceable talents as keys to a harmonious marriage.
Marriage is the fulfillment of many basic human needs. It satisfies the natural attraction men and women feel towards each other and provides people with a sense of stability. It also creates a suitable environment for having and raising children.
At this juncture, the couple declares that their marriage actually has a higher goal and purpose than satisfying their own needs and desires. "All was created for G‑d's glory," and this event is no exception to the rule.
"All was created for G‑d's glory," including — or perhaps especially — the Jewish home. Judaism doesn't allow for a separation of powers — i.e. G‑d and spirituality being relegated to the synagogue, with the home being the domain of personal ambitions, hobbies and priorities. This blessing is an expression of the couple's intent to establish a Jewish home predicated on spiritual values. A home whose goal it will be to be a bastion of light, Torah and mitzvot; a home devoted to G‑d's glory.