It keeps teams from having a super aggressive fuel map to switch to get into position, followed by switching to a fuel-sipping engine map to just stay where they are for the rest of the race. If that helps prevent F1 races from doing the normal thing of 5 LAPS OF FURIOUS ACTION then follow the leader to the finish, I'm all for it.
Surely if you limit boost pressure and rpm it would take care of that better? The map to increase hp at a given boost pressure involves injecting slightly less fuel and advancing timing.