Thought definitely uses language, but it transcends language and doesn't need it.
Then why do I use it? I am pretty sure that the part of me listening needs the words to understand what another part of me is saying. I dont think I am unique in this matter... There are other ways of communicating in the mind/brain: forms/shapes, more or less vague "sounds" etc
But without language it would be hard to think about intellektual matters.
I think there are benefits to different kinds of thinking. Going over something verbally helps in some ways, hinders in others. Certainly you can tell people to think about problems in different ways, and then measure the difference in performance. What you're in effect doing is treating your own thought process as if it were an input - as if you were hearing it from someone else, and then judging it and refining it on that basis.
There has been the idea floated that the mind originated as a social simulator - a specialist system for simulating the actions of others in response to our own actions. That then leads to the ability to model our own actions, model what other people are likely think we're going to do, and thus self-awareness of ourselves as a social individual. This has the interesting side-effect of allowing us to model the physical world as well, leading to science, technology, and civilisation as we know it, albeit with a tendency to treat anything we don't understand as a person.