This gets asked a lot. If you're interested, do it. If you're not, then don't. Simple.
I think that ECs really do matter but I've had a hard time communicating the nuances of this in past threads. This is the best I've come up with:
The ideal resident applicant is the sort of person who, in addition to great numbers, is also a really interesting and cool person who makes time to give back, gets involved in things they care about, produces good research, unselfishly cares about others, and gives 110% without complaining. This kind of person will likely have a certain kind of CV that reflects their values and work ethic. In this way, the things on their CV "matter" because they communicate what kind of person they truly are, not because any one item is particularly valued on its own.
Conversely, trying to pretend to be this kind of person by accumulating enough CV fluff is not likely to be very successful. Doing something because it truly interests you is the kind of thing that may lead to other opportunities and help build a CV that tells a story about a passionate and hard working person. Doing something because you hope it looks good on a CV is probably not going to have the same effect.
Still a difficult nuanced point, but hopefully this makes sense.