Easy: a walled garden is much more valuable to its operator, and sharing the data would reduce (potential) profits. In other words, only Google can use the data

Easy: a walled garden is much more valuable to its operator, and sharing the data would reduce (potential) profits. In other words, only Google can use the data it gets from its Waze, which gives it a competitive advantage. Oh, you mean downsides to users? Never mind ;)