Game days are scripted, yes. There was a period from about 2004-2013 that the reigns were yanked pretty hard on band and yells. With personnel changes, the decision was made for the 2014 season to give FTAB and yells much more leeway. This season is no different.
The problem lies in that they are given the option. Meaning, they have the option not to play or yell. If they exercise the option against, there isn't much that can be done. The pump-up music was bought in to fill in the times that they choose to nothing. Or, as was pointed out, to fill in the rest of the time on TV timeouts. Four minutes is a long time to yell and most of FTAB's songs are only about two minutes.