Google first announced plans to add immersive views to Maps during its I/O developer conference in May of last year. The company began the initial rollout in July with photorealistic 3D aerial views of around 100 popular landmarks worldwide. You could see the Empire State Building in New York City, Big Ben in London, Alcatraz in San Francisco, and the Tokyo Skytree in a whole new light.
Immersive View on Google Maps necessitates a large amount of data and city information. This is most likely why the company is taking so long to roll out the feature worldwide. Immersive city exploration View consumes approximately 2GB of data in 30 minutes.