Why does it feel like the internet is getting less social? First Yahoo Messenger got shut down, then MSN Messenger, then AOL Messenger...?

Time.  Things change with time.  Companies come about, and a bigger company with tons of money says to a smaller company, hey we want to purchase you for $50 million.  Well, if that smaller company isn't really making a profit from their business 10 years down the road, they're going to see that $50 million as a benefit to them, and who cares about the general public using their services?

That's how they look at it.  AOL was on the decline once cable internet started coming around.  When new websites started popping up for people to access, they no longer needed AOL.  Yahoo Messenger was shut down, I would surmise it is because other programs like Skype came about, but also internal changes at Yahoo, and some higher up saying Yahoo Messenger doesn't make a profit, or it isn't used like it used to be.

Yea, it sucks, but it's the way of the world unfortunately.