The scenario I had in mind was a long show where other unions with minimum call times come into play.
Suppose you've got a house with no crossover, or the crossover requires lengthy travel, outdoor travel, etc. Not uncommon. Anyone starting SL has to be at places by 5 minutes, while anyone starting SR can head out at 3m, since they can only cross when the main rag is in.
Now, suppose this messed up house decides to do a show that's say, 3h and 30 minutes if everything goes according to schedule. You've got stagehands and/or orchestra on a 3.5 hour minimum call, and after that the entire crew & orch get paid by the hour. A lag on start time could get very pricy for the theatre at that point.
See this
IATSE agreement (warning: large PDF), top of page 6 for an example of such an agreement.
While I don't deny that there are problems higher up on the food chain if they're running that close to the minimum call limit, it isn't totally farfetched for me to see a company blaming the stage manager for the extra cost instead of fixing the real problem of excessive risk-taking.