Can't the same be said about saying no based on a picture (and even more so)?
I'm not sure if I understand what you are Implying.
You can't convey a soul or emotions via a photo, or via research, it needs to be experienced firsthand by the couple, and it often takes more than a 1st outing to see it.
Research done well will highlight the obvious compatibilities and vice versa, but never to the point that a photo can seal the deal.
Edit: "research done well" is a larger problem than photos IMO, and it's much harder to educate the parents who are all grown up, then the young adults.