Language is useful. (Though it would be less so if people didn't automatically assume being nonverbal made you completely stupid. Picture boards!) It doesn't follow that we have to think exclusively in words. Language is not a very basic part of Amanda Baggs's thought processes, for example.
Thinking without words is useful because it's (sometimes) fast, and has different constraints.
Before language, people must have thought without words. I often have the impression that I have a thought fully-formed in my head, yet I wait to listen to it unfold in words before moving on to the next thought. Perhaps I could think much faster if I weren't addicted to words.
Has anyone developed techniques for thinking without words?
This would have a little in common with Buddhist practices of emptying your mind, but wouldn't be the same thing. For one thing, Buddhists also try to empty their minds of images. More importantly, they are trying not to think, while I'm trying to think - just not unpack everything into words.