Cool is a byproduct 

Happy Cog's Joe Rinaldi on the obsession with "cool":

Cool just happens; it shouldn’t be the target a project tries to hit. I don’t think great work and being cool are mutually exclusive. I think a lot of creative agencies are cool. But here’s the thing: the coolest agencies I know do great work with some excellent people, thus they are cool. They don’t have to spend a lot of time or effort convincing you how cool they are. Sure, they may have a foosball table (almost a requirement for creative agencies these days), but it doesn’t have to be the first thing you see when you walk in the door. It’s a company’s work that makes them cool; their output, not their amenities.

What he doesn't say is how it's possible for people or groups to create the appearance of coolness through foosball tables or company beer bashes, and how that isn't just different from making cool work, but can be actively harmful. Part of making great stuff is listening/observing what doesn't work, then fixing it. Cool is finding one ridiculously meaningful improvement in a product that only took you ten minutes, but meets the need so well that you come off looking like a genius. You can only achieve that by listening, and self-consciously cool people are too busy listening to themselves to listen to anyone else.

Plus, there's always the risk that by trying too hard to be cool you come off looking like total jackasses.