Why should you use ABTS when measuring the concentration of an antioxidant in a biological sample?

For example, can you explain the concept behind your Amplite® Colorimetric Antioxidant Assay Kit (Cat# 15900)?

Quantitating antioxidant activity in a biological sample provides vital information regarding the cells ability to combat damages induced by reactive oxygen species (ROS). 

Our Amplite® Colorimetric Antioxidant Assay Kit utilizes ABTS (2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonate) as a colorimetric indicator to monitor antioxidant activity. In the presence of horseradish peroxidase (HRP) and hydrogen peroxide (H₂O₂), ABTS is oxidized into the water soluble chromogen ABTS⁺. ABTS⁺ can be monitored spectrophotometrically at 405 nm. The absorbance suppressed in the test samples will be proportional to the concentrations of the antioxidants in those samples.