This may be a generational thing, but I prefer my workplaces to be for work, and my playgrounds to be for play, without blurring the lines between them.

Leaving work at 5 pm is the goal. Clock out. Go. Be free.

If I want a social club, it will be a separate organization. People staying at the office after hours is indicative of a toxic work culture (unless those folks always come in just as late on the other end of the workday). An effort to design a workplace as having the appearance of fun strikes me as disingenuous, at best, and at worst is a signal that the company is, as David Brent put it, "'aving a larf", at the expense of the investors.

Do not make your offices fun. Levity and gravitas can co-exist, but at work, the latter should have the greater weight.