What is the advantage of using imprecise representations of time i. e. ‘an hour ago’?

I see more and more that messengers like Skype forego precise timestamps and display things like 'just now' for messages younger than 5 minutes.

The same holds true for YouTube videos, that show '1 week ago' or '1 month ago' in the video overview of a channel page.

I find this incredibly irritating. What value is this supposed to have?