There is a blinding error when it come to cop shows

On the lookout for a suspect, spotted, with cops yell out the suspects name, then the police department they are with, stop, put your hands behind your head, etc.
All this from 30/40/50 meters away. Giving the suspect ample time to make a dash for freedom.
Why do they not nonchalantly walk along, showing no interest in the suspect, then nab the person?
Yeah, yeah, chases are suppose to make it more exciting, yada yada yada.
Many times the suspect gets away.