[FREE][STEAM] The Search (13 April – 14 April)

One big difference is that this "deal" isn't even available yet. The bundle threads, with the exception of Groupees and their blind buy garbage, pop up once the content of the bundle is known and purchases are available, or very shortly beforehand, so they convey immediately useful information. Meanwhile, we could post here for another week and it would still be too early for this post to exist.

Another big difference is that these are individual games. Imagine if, for every bundle, a thread got posted for each individual game with the titles:
[STEAM] Super Meat Boy and 7 other games - $4.99
[STEAM] Gish and 7 other games - $4.99
[STEAM] Fez and 7 other games - $4.99
And so on. It would be a ridiculous and spammy way to convey the information when you could just say "Humble Indie Bundle, 8 games".

A third big difference is that, with the exception of Fanatical, most bundle sites don't release multiple bundles at once, so there's no big flood of them all on the same day. And Fanatical does get a megathread for their bundlefests sometimes, to help keep the spam down.