Does size really matter?

I got into a debate with someone today about women and the size of engagement rings. To set up the story, somebody that I and the debator both know has a gorgeous engagement ring. As I love engagements/weddings/marriage, and this was the first time I had seen her ring, I congratulated her on her engagement and upcoming nuptials. This ring was easily 1 carat, but her response; I want bigger. The person I argued with started laughing and I asked him why. . . his response; "Women ALWAYS want bigger rings." I quickly refuted that one with my own story. I would have accepted my husband's proposal with no ring, he was the one who said I deserved one. But I said it years ago and I mean it now, I didn't need a big ring or any ring at all, I just wanted Robert.
It's not just this little story. There's hundreds of commercials emphasizing the importance of the engagement ring; like Tiffany's print ads where they never show less than a 1 carat ring; or those radio commercials that warn against buying a "dinky diamond." The fact of the matter is, a ring doesn't make a marriage. When you've had a bad day at work or you fell out with your best friend, a big ring isn't going to make you feel better; your husband is. So why so much emphasize on the ring?
I don't want anyone to misread what I'm saying. I'm not criticising any woman that wants a big ring. I'm just not sure why there's such a focus on them when, in my opinion, the most important part of any marriage is the relationship you have with your husband.