Of course, that does not necessarily mean that 2 billion people use Chrome every day on their devices — just that there are 2 billion installs. The latest statistic for active Chrome users remains at 1 billion, although that statistic is getting old at this point — it was released in April.
Google has seven services used by over a billion users. Those include Gmail, Android, Maps, Search, YouTube, and, as mentioned, Chrome. It seems like Google is increasingly racing itself to get installs on its devices.
The number of Chrome users is certainly helped by the fact that it comes pre-installed on plenty of Android phones and that it plays well with other Google services. But there is also something to say for the fact that it is simply a great browser. Sure, the likes of Firefox and Safari are pretty great browsers too, but Chrome was one of the first to implement things like browser plugins, infinitely expanding its use.
That does not mean Chrome is perfect and if Google wants to stay on top, it will definitely have to keep up with making changes to the browser. Perhaps the worst thing about Chrome is that it is relatively power-hungry, especially on a Mac. Still, Google has been making improvements to Chrome for Mac to improve how much processing power it uses up and that is only likely to continue.