In March 19, 2002, a fan was struck by a puck and killed behind the glass because there was nothing protecting a shot from going over the glass.
The commissioner at the time made it mandatory that safety nets be installed to protect the fans from pucks coming blazing towards them and not being protected.
As technology was advancing in the mid 1900's, TV's were on the rise.
if you wanted to see a hockey game, you would have to go to the rink and watch it live.
In 1952, the first NHL game was broadcast to those who owned TV's.
This made watching hockey much easier for those who didn't want to have to go watch they game in person, but could watch it in the comfort of their own home.