That's just the coverage available on one particular website. (Other sites can have different data sources and different coverage.) Also, those rectangles just mean that there is some coverage within the rectangle. (Often, coverage is available around larger cities and a lot of the area is not covered.)
Furthermore, AIS is sometimes used for collision avoidance, so it is used for safety.
Whether or not you were ever a fan, it was a sad scene.
That's just capitalism. The sad thing is that the same thing is not happening to failed banks, insurance companies and investment companies.
What is now proved was once only imagin'd. -- William Blake