Graham Gibbs at the University of Huddersfield has a number of very useful YouTube videos on research methods, particularly focusing on qualitative research. In this video, he discusses transcription for qualitative research and some of the issues involved in this. 

"Given the nature of transcription, why do it? The reason we do it is because usually we find it much easier to work with a transcript rather than a recording. […] For analysis purposes, people still find it easier to work with a transcript, despite the effort that goes into creating transcripts. The reason has to do with the fact that you can move around transcripts – you can mark it with a pencil; you can shuffle the pages very quickly and find the bits you want. You’ve got very quick, random access to what you want. You can remember bits because you’ve marked them very easily. […] I’m afraid that transcription is still the norm for anything that involves interviews or recordings."