We just can't promise the stability of the server. It both concerned the number of calls causing load to the server, and the lower time limit means there's less time to deal with potential server hiccups. That means we're causing the staff more effort to handle the fallout of those games that need to be cancelled or their points returned.
Just play your three minute turns faster.
“This is how humans are: We question all our beliefs, except for the ones that we really believe in, and those we never think to question.”
- Speaker for the Dead, O.S. Card