How many 1st base coaches have been killed by line drives? Yet all of them have to wear helmets.
The last one I recall was at an Arkansas Traveler's game. My son (9 at the time) was standing on the first base fence because they were going to allow the kids to run the bases between innings. The coach had turned his back to walk farther back in the coaching box and was caught by a liner just below the edge of the helmet.
I don't have an issue with the net. Have been behind netting a lot including all of my son's high school games and never really notice unless I'm trying to take pics and the auto focus sees the net.
That being said, the net is a reaction to public pressure not public risk. I tried to pull info from some salient publications.
About 53,000 of the 73,000 fouls hit each season enter the seats, according to Edwin Comber, creator of foulballz.com.
Totaling data from multiple sources, there were about 750 injuries reported to stadium first-aid booths at games attended by approximately 31.6 million spectators.
That translates into 23.7 injuries per million attendees -- or an estimated 1,756 injuries last season, when 74 million people went to games. (Bloomberg Business)
Since the 1969 with the advent of larger steeper stadiums, there have been 21 non suicide deadly falls at U.S. baseball stadiums. Most of these are from the stairwells including jumping from platform to platform on more than one occasion. Alcohol plays a role in a majority of those.
It would seem they need to heighten the rails in the stadiums and along the stairs as much as they need to add a net.