The point was that DRLs make the car more visible than no illumination, which means they catch the eye easier and can make the difference between spotting a car in your periphery, or not. There is no dispute that a car with DRLs will be easier to spot than a car with no lights, and saying that you should be able to see an unilluminated car in daylight is no argument against not adopting them.
Yup, I do understand dusk and dawn....evidently you don't though, because the very definitions of dusk and dawn are, respectively, those periods of twilight when the sun is not above the horizon. So whether you use your lights at these times or not is irrelevant - I'm talking about once the sun is over the horizon, and it's pretty much broad daylight, but it's still low enough to be directly in your eyeline if your heading east/west.
For the record "sport", I ensure my headlights are on at these times, but again, the point is that many people won't because it's daylight, so they don't think. DRLs at least mean these people will be more visible in your mirrors.
I absolutely agree, but whilst we have a road network that is infested with such people, and whilst DRLs have pretty much no disadvantages, I'll continue to consider their adoption a good idea.