Why are wedding anniversaries acceptable to celebrate but not birthday anniversaries?

Why celebrate wedding anniversaries but not birthday anniversaries?

Because there are no pagan origins connected to marriage. Marriage was divinely instituted by the "one true God"...Jehovah. (Genesis 2:18-24; Matthew 19:4-6; John 17:3)

Unlike the mentioned examples of birthday celebrations, the Bible does not put marriage in a bad light. Jesus himself both attended a marriage celebration and contributed to the pleasure of the occasion.—John 2:1-11.

"It thus would not be strange that a couple might on their wedding anniversary take time to reflect on the joyfulness of that event and on their resolve to work for success as a couple. Whether they focus on this happy occasion in private, just as a couple, or they have a few relatives or close friends with them would be for them to decide. The occasion should not become a mere excuse for a large social gathering. On this occasion Christians would want to be guided by the principles that apply every day of their lives. So whether one takes note of a wedding anniversary or not is a personal matter.—Romans 13:13, 14." -Watchtower 10/15/98