Why would my 'ABS' light stay on?

This indicates there is a failure in the Anti-lock brake system. Unfortunately, the only way to know what the problem could be, would be to have the ABS system scanned for fault codes. This requires a scanner capable of reading Chassis codes. Typical faults are Wheel Speed Sensors and Control Module (EBCM).

ABS light on means some fault codes stored in the ABS, you should get a airbag reset tool with your car.