There's a software lifecycle. At the beginning of a software project, nobody knows anything about what to do, because (if the market niche isn't already filled) nobody has done it before. Python and Ruby are great for that. Then as the software grows up, the requirements become more well-known, and more people start using it, you need to transition to more maintainable code that runs more quickly. Go is ideal for companies in that growth stage - it runs fast, it's easy to communicate what the code does, it doesn't allow a lot of tricks that can trip up other developers, and it encourages relatively robust code. Once you get to the massive scale stage like Google you probably need to be in C++ anyway, but by definition growth companies are where a lot of the action is.