A good way of showing respect to the reader is by informing the reader approximately how much of their time will be taken up by reading your blog post, essay or presentation. It can also lead to better engagement by confirming that the user has time to read the content in full or allowing users to bookmark the content until a better time is available.
Similarly, the speaking time can be used to estimate the duration of a presentation or meeting. This can be particularly useful when the meeting or presentation must be completed within a specific timeframe.