Not to mention you can enhance all sorts of playback stuff. Simple one: Subtitles. Netflix took forever to add subtitles, and even now the coverage is spotty, and languages are very limited. And if sync is off, tough luck.

Also, if there's any problem with playback, you can fix it. A few things I use often: Brightness control, dynamic range compression (nighttime mode), subwoofer support (2 channel audio on Windows just goes out L and R; ffdshow lets me easily split low freqs to the sub).