Are there any safety or technical reason airlines do not display flight information to passengers in real-time?
If data is continually updated, nervous flyers will fixate on every minor change.


The altitude changed by 30 ft in one second?That is a descent rate of 1,800 FPM!  Surely we're going to crash!
The speed changed from 480kts to 470kts in one second?At this rate, we will stall in less than a minute! 
The plane was at 260kts at 9,800ft?
This crazy pilot is breaking FAA regulations and must be reported!


By updating less frequently, there is a natural filtering and smoothing of the data to obscure tiny measurement changes due to instrument limitations or conditions like turbulence.