Auto industry? I'm assuming you mean self driving cars, which, at this point, are still in the concept phase. Space industry? Did I miss something, is Google launching rockets?
There are many other companies that are way more diversified than Google.
http://en.wikipedia.org/wiki/General_Electric
http://en.wikipedia.org/wiki/Siemens
http://en.wikipedia.org/wiki/Yamaha_Corporation
Plus, expanding into a wireless carrier makes way more sense for Google than any of their other ventures. One of the limiting factors of internet use in the first-world is terrible carriers with data caps.