Because InfectiousDesigner will do it better, and has done so for years. The new short film Half-Life: Origins even proves that point.
There's nothing more depressing than to see an awesome gaming franchise being torn apart by horrible writing, horrible acting and a lack of proper vision in an embarrassing Hollywood translation. It's as if producers, directors, story writers and screenplay writers have absolutely no idea what a gaming console does, and has no desire to do the proper research so that the resulting film is just as genuine as the source material.
That said, what Hollywood needs is writers, directors and producers that actually live and breathe games. A prime example would be InfectiousDesigner who have been creating Half-Life live-action clips for years. They're not half-baked fan-based clips made in the backyard either, but full-blown short films combining live action and CG environments and elements.
The latest short film from InfectiousDesigner is a remake of the original Half-Life's opening sequence. "After 10+ years since it's release, if you ever go back and replay the original Half-Life, it doesn't look anything like you remember," the director explains. "The graphics are horrible compared to present day games, but years ago it blew my mind. This video plays with that contrast. I incorporated a fusion of live action and CG environments that give it a semi-realistic look, but also not realistic at the same time."
Valve, you seriously need to let this team create a full-blown theatrical release...