Communication is necessary for a healthy and fulfilling relationship. Even more than attraction, because people can be more attracted to each other than any couple ever has in the history of life but if they can't communicate their dreams, desires, strengths, weaknesses, etc. their relationship is destined to fail.
A couple needs to be able to express themselves to each other.
If someone disagrees with their partner about something, being open and discussing that disagreement can save the couple from an argument.
When a holiday is coming, the couple that communicates is more likely to know exactly the kind of gift their partner wants -- whether it is specific or a surprise.
Sex is better for the couple that knows what the other wants. Not predicts. Knows. And the only way to know is if you either find out by chance during sex or you find out for sure during conversation. It may sound silly to some to tell your partner exactly what you want sexually, but the satisfaction you both get from knowing what the other wants will make that communication worth it.
Communication allows couples to work together to solve individual problems and relationship issues. Communication invites a couple to build goals they can work towards -- thus enhancing their relationship.
Communication isn't just one component of a successful relationship, it is the most necessary component.