Not having to continually train people is one good reason.
It also does well for productivity and morale when people can plan years out in advance as a regular employee - versus worrying if their 3 month contract will be renewed. Instead of worrying about life, things get done.
Candy dispensers and air hockey are gimmicks. They do not provide long term fulfillment within an organization. The article identifies high turnover rates. I believe it's extremely tough to be successful without stability in the org.