Why do some people pull over when an emergency vehicle using lights and siren is coming from the opposite direction?

Section 3325 of the Pennsylvania Vehicle Code requires drivers of all vehicles to yield the right-of-way to the immediate approach of all emergency vehicles utilizing approved audible and visual warning systems.  Drivers that pull over when an emergency vehicle utilizing audible and visual warning systems approaches from the opposite direction are being safe drivers.  They are also obeying the law.