You actually end up talking to people and getting to know strangers, an interaction that is oftentimes marked by animosity (even hostility) when people are matchmade with other people using an automated system. In Revelations 2, the host player has to add the other player as a friend on Steam - and then manually invite the newly added friend to a game he hosts on his client. This affair takes effort to co-ordinate and it also makes it more personal. So far I've met people from Canada, United States, Australia and even Malaysia. I felt kind of good, being able to properly communicate and co-op with people using this old school way. It's a nice way to workaround an otherwise "dead" community, and people are more likely to feel more responsible and accountable for how they interact with each other.
In the past, I've had similarly positive experiences with Nintendo's friend code system for Pokemon trading. Everyone had to add each other's friend codes, and everyone that I battled and traded with were very cool individuals. Maybe it has something to do with the fact that people have to interact with one another prior to adding someone to the friends list, or maybe the fact that they made an effort to add you means that they give you much more of a benefit of the doubt. Might even have to do with the permanence of them having you on their steam/nintendo friends list. Automated matchmaking systems are still the most efficient, and effective way for bringing gamers together, but manual co-op invite/friending systems have the more superior quality of interaction between individuals.
Picture credit: Kingofshadows26@Deviantart