Many companies get half the equation right..
They have a "cool" culture, but lower standards for who they hire. But here's the thing.. when you have average employees, it demotivates your superstar employees. It's annoying working with people who aren't good at their job. No amount of ping pong tables, onsite day-care, or free catered lunches can overcome the soul-sucking torment of working with idiots.
It's the same dynamic as group projects in high school. There was usually one person who did all the work, but the credit was shared equally. No one should be subsidizing anyone else's lack of effort.
If a company gets both right, it is inspiring because it is rare.
If you hire average employees, even if they're fun to hang out with, it poisons the competency culture which is a very real part of company culture. The competency culture is simply, the expectation of excellence.
Many companies talk about it. Few actually enforce it.
There's a certain amount of pride in knowing that you're a member of a tribe that doesn't hire idiots. It's a subtle reminder that you are not an idiot, or you couldn't have gotten a job there.
This is emotionally satisfying and working with competent people is it's own reward.