Open Skype? Not online. Check Facebook, nope, they're not on. Messenger? Nope. Ok, I'll open my contact book, and get their number to call.
Wouldn't it make more sense to simply select the person I'm trying to reach, and see what platforms they're online, so I can choose my contact method?
Or what if I want to see what's new with one friend? I should be able to click their name, and see their facebook changes, new tweets, status updates, etc.
Of course, this isn't always the case, I might want to open Facebook without plans to browse a particular person, or I might open Skype just to see who's online that I can video call.
So, there are times when I need to take both routes. They should both be available so I can choose either. It's complicated to aggregate content from a variety of sources into a single page, so it's not a surprise why this option isn't frequently available. You would almost need a new standard, so HN could provide an API for a user's comments, posts, etc, and Facebook, Twitter, Reddit, etc, all do the same. Then I can build an app that merges all of this information together. So a user opens the app, and creates a page for John, enters John's Facebook profile, Twitter/Reddit/HN handles, and everything appears in a single place. However, these sources then get less direct traffic, and therefore less revenue, so it's unlikely they would jump on-board.