Timestamping plays an important role when you want to listen to the original audio when reading transcripts. Texts are sometimes emotionless but audio isn't. It is therefore helpful to play back to the sentence and check if the speaker was serious or mocking.
Timestamping can also be useful when specifically referring to a deposition is needed. For example, Ms. Vasquez: “[...] play the portion from 157:21 through 158:54. It’s a recording. [...]”