Rules like this will flesh out in the officiating. How many hip drop tackles were intended by the tackler in a pre-penalty environment? How many are bad luck?
The reality is the NFL owners are billionaires who want to appear they care about the health of players. These are the same people that do not want Americans to have a workable affordable healthcare system. To the owners the players are assets. They prefer their assets operable to profit from higher ratings when stars play. They prefer to avoid lawsuits from retired players not include additional "but you could have passed a rule to stop..." phrases in some future courtroom scenario. If we need to ask why the NFL passed a rule, the answer is because the billionaire owners think it profits them.