My thoughts are very much in line with @lindagaf. In the conversations that I’ve had with people who have worked in college admissions offices (AO, DA) at very selective schools, they have indicated that they receive high stats applications in numbers that are MULTIPLES of the number of seats they have in their classes. They need a way to differentiate among all these strong applicants, and one way to do this is to be “nationally, or even internationally recognized” in some way. As one DA put it “When you were in school, to have been a varsity starter in a sport – or better yet, two – would have been enough. What stands out now is the applicant who was on a national team!” So yes, an EC at that level – which includes Intel awards, etc. – is really helpful because it allows your application to be easily differentiated from the others.
Most of us, though, aren’t quite that “special”. The garden variety of ECs – MUN, JSA, varsity (non-recruited) athlete, volunteer – are more like the high stats in that they are expected (but probably not in the quantity that most of the people who post “chance me” requests imagine). Top schools want to see kids who can engage outside the classroom and ANY kind of EC shows that. They also offer experiential learning. Few ECs probably allow the application to quickly separate itself from the rest of the pile but they can provide a backdrop for explaining who you are.
Personally, I think that the kid who can tell a good story about who he/she is – and this is done primarily through the essays, the LORs, the interviews, AND ECs –the one who can “come to life”, is the one who stands the best chance of being admitted. After applicants have jumped the various hurdles (stats, scores, some level of involvement) for whatever “bucket” they are filling (gender, geography, etc.), the one that the reader can most easily advocate for in committee will be the one who gets in. And it’s easier to advocate for a person than a package of stats. I HATED how often on tours and info sessions someone would prattle on about how they wanted to see “passion”. While some kids have found their “thing” by 17, plenty have not and need/want college to help them do that. But to the extent that “passion” lends consistency to the picture, it helps. The kid who volunteers at the animal shelter, trains agility dogs, has a summer job with a groomer, and wants to be a vet is easy (at least for me) to envision as a person. (The theme doesn’t have to be this explicit, but you see what I’m getting at.) I don’t know that it has to be something terribly unusual, but it helps if it all hangs together.
A DA of one of top programs said that one of the things that she always looked for was whether the whole application “came together.” If a kid goes on about how he’s a team player and the LOR talks about how the kid has solved amazing problems alone, that could be a red flag. ECs are important in that they can further “reflect” who the kid says he/she is. The kid who is the team captain – having been elected by peers specifically to provide leadership to the rest of the group – implies certain traits. IF these are consistent with the rest of the app – ability to relate to and inspire others, willingness to work hard against the odds, etc., I’d guess it would help.
So to answer the question, yes, they are important in showing that you have a life outside of academics and they add color to the application. That is why it’s important to do things that interest you rather than things that you think will look good. You’ll be able to explain them without too much thought.
For students applying to LACs, where everyone is expected to fill a couple of roles to both knit the community together and to ensure that sports teams and the orchestra both have full rosters, ECs will show that you can be that person and they can be important in that regard – but again, in showing who you are.