So, just my experience here. You don't just get hired at a job, or especially for a contract, based on your resume. For one thing, resumes (and job interviews) can be faked. Also, no matter how good your skills, this still leaves the question of whether or not you _want_ to do a good job, or if you'd rather do whatever gets you ahead in the moment.

In the long run, I have found that good relationships (doesn't have to really be "friendships", but at least pleasant working relationships) advances one's career, because then the person has reason to believe you won't knife them in the back the first time it's to your short term advantage to do so. If they ask you for help with a work problem, will you just help them fix whatever it is, or try to make sure everyone else sees you fixing their screwup so you look better (and they look worse)? If they need to discuss a half-formed idea with someone, will you help them thrash out the pros and cons, or will you use the fact that their idea wasn't fully baked, or maybe was even fatally flawed, to show everyone in the workplace that you are smart and they are not as smart? It is a lot easier, and a lot more productive, to work with people who you can trust to at least somewhat care about your well being.

None of this means you have to be attending their wedding or godparent to their kids. But if you have a few beers (or whatever) once in a while, it builds some trust that helps people work together more productively. Like unit tests in code, or payments for insurance, or time spent on safety, in the ordinary course of things the payoff is not obvious, but good working relationships help out a lot, and a basic minimum of socializing helps establish that.

Again, just my anecdotal experience.