Playing devil's advocate here, I'd guess that it's because sprinting is a relatively violent activity compared to normal cardiovascular running, which relies pretty heavily on the core for stabilization and rotation of the trunk of the body with respect to the hips. It creates a lot of compression and torsion forces throughout the spinal column.
And normally the power lifts (cleans, push press) are pretty integral to a sprinter's muscular development, so you could say that on an anecdotal basis that if you aren't in good enough physical health to perform exercises for training for a specific athletic event, it may not be a good idea to perform that event... though that doesn't always hold water for every type of athletic activity.
In the end I still think that if you don't feel that you are injuring yourself further, or delaying the healing process, there's no reason that you shouldn't be able to perform sprints.