These rules were put in place because in 2004 someone got knocked out after being hit in the head with a HW flipper. It could easily have killed him, and at the time thought it may have.
Since then the locking bars have been used and in the rules, and have cut down safety issues massively. Just sometimes the get overlooked and that needs to be enforced better.
It's up to roboteer's as much as it is event organisers to make sure your in the rules.