They are infringing in the same way as pen and paper companies are infringing when you hand-write the contents of an audiobook on paper for personal consumption. I believe that most people would consider this being an allowable thing to do.

Pen and paper companies sell you tools/materials to create works. They don't know or care what you create with those works. For all they care, you could just eat the pen and paper. Importantly to this example: they don't transcribe the audio--you do. Your transcription is a derivative work and if a fair use exception does not apply, would be copyright infringement if the copyright owner cared to enforce it in these circumstances.

Amazon's Kindle transcribes the audio of an audiobook using software created by its programmers for the sole purpose of transcribing audiobooks. You don't do anything. Amazon does all the work, at your request. And that makes all the difference, because what Amazon is doing has pecuniary value and thus fair use would not apply to their actions.

I believe that most people would consider this being an allowable thing to do.

Most people also believe it's okay to speed. It's still against the law and it's not a defense to a speeding ticket when you get caught.