Roughing the passer is an infraction designed to protect the Quarterback from the most vulnerable position on the field. It is more often called now because of the huge contracts these players command. It might seem like it’s designed for prevention of injury, but it’s purely for commercial reasons. The fact that it might prevent injury is only an ancillary benefit.  

When we get roughed up in our field of play, there is no referee to penalize the miscreant. However it is our ability to stand right back up that commands the respect for ourselves and of others that might do us harm, whether it be by design or by happenstance.