It has become a target for many but 10,000 is not based on any scientific research, it is completely arbitrary. The target originates from a successful Japanese marketing campaign following the Tokyo Olympics in 1964.
Public Health Guidelines suggest 30 minutes of moderate exercise per day so a minimum of 7,500 steps will get you there but there is no research to tell us the benefits of more steps.
Not taking into account the intensity is the major problems with a just a 10,000 target. Doctors will tell you any exercise will help but a minimum of 30 minutes at an increased heart rate (brisk walking) is important.