I am married and I agree with the OP. I don't see it as a huge achievement and people who do are the ones who, in my experience, like to spend spend way too much (IMO) on a wedding. But we're proving his point really by discussing it!
Having experiences that suggest that an achievement is likely very minor should not be a cause for withholding congratulations, or any other social pleasantry. For example, in my experience, just being accepted to college at all is really not much of an achievement. There are plenty of colleges that will accept virtually anybody who applies. However, if a friend or coworker were to announce one morning, "I was just accepted to $LOCAL_COMMUNITY_COLLEGE," I would congratulate them. Maybe the hardest part for them was applying in the first place. Maybe it was harder for them to just apply to that college than it would be for you or I to get accepted into Harvard. We can't know, so we err on the side of warmth and encouragement.
As for,
> But we're proving his point really by discussing it!
