I guarantee you no one had that thought because it's ridiculous.

: Putting it on XBL? "Why isn't it selling Millions of copies!?"

That's probably closer to the truth.

: Steam looks like a good way to make a profit on a messy release. The $5 price
: tag makes it evident that the tarnished Halo name alone is not enough to
: overcharge people on what is essentially a mobile game. Isn't it $3 on
: Windows phones or some such?

Apparently it's $6.99 on Windows 8 and Windows Phone 8.
Anyway, there's no way they would do this if Games for Windows Live was still around. It's nice to see Microfost fail at something and then use a competitor's stuff.