Google has the money for a proper advertising campaign. Who knows, once the final version goes out (it's still BETA, isn't it?), they may start to push the thing properly.
Also, there's not really a trend with the browsers with time. Opera has been around for over a decade now, and still sits just under 1%, Firefox has been having steady year-on-year growth since inception, and Safari's is pretty much dependant on Mac sales (as the Windows version is just a no-go).







