"What's New!" in my Steam Library just notified me about an update for a game I hadn't installed.
That was a great thing—I just installed it again to try it out!

But this rarely happens: I hardly ever get to know about updates for my uninstalled games... and often, I don't even want to see what they're doing cluttering up my library!

What I suggest is this:
Add a dedicated place in Steam where you can see a list like:
"This game had 15 updates since you uninstalled it, with the last one on ..."
Or even a general stats overview showing update history for every game you own!