There are many more variables to be considered, controlled and adjudicated in the mind of the shooter when you're actually sending a pellet from Point A to Point B as precisely as possible.
Laser tag merely tests one's abilities to align the sights. In real marksmanship, that's merely the starting point.
Actually with a simulated laser equipped weapon, there are statistical optical effects which also lend a certain amount of randomness.
This was analyzed 20+ years ago for the military as they were designing the MILES (Multiple Integrated Laser Engagement System) for simulated-fire live training.
The computers attached to the optical sensors on soldiers and other targets intentionally add in more randomness in their determination of a kill, from so-called probability-of-kill tables. Of course, they have the option of not doing this for Olympic competition.