NO COLOR vs COLOR isn't the same as "n 3D cues" vs "n+1 3D cues".
A better analogy would be
"All colors apart from a particular shade of purple" vs "all colors".
Of course the current systems are rubbish, so you're getting an extra 3D visual cue at the expense of clarity sharpness brightness. And headaches thrown in to boot.
We're just talking degrees of (what we perceive as) realism. The fact that the technology hasn't caught up yet is no reason to dismiss the entire idea.
Think about Technicolor, for instance. Unrealistic, and to some, headache-inducing. But it was an early step toward what we have today.
These days, most films are shot in color, and in a fairly naturalistic way that people don't generally notice. But that certainly doesn't mean there's "no point in having it there." It's just a greater level of immersion, which helps draw people even further into what actually matters (for most films): the story, the characters, etc.
Maybe I'm biased. I wear glasses and have a 'bad' eye and a 'good' one. Also I can't see those stereoscopic pictures etc. It's lost on me unless it's made really obvious, which is what they've done in the movies I've seen in 3D - which ruins it.
NO COLOR vs COLOR isn't the same as "n 3D cues" vs "n+1 3D cues".
A better analogy would be
"All colors apart from a particular shade of purple" vs "all colors".
Of course the current systems are rubbish, so you're getting an extra 3D visual cue at the expense of clarity sharpness brightness. And headaches thrown in to boot.