wellAlbidarned
International Coach
Regarding the topic - helmets had a huge impact on batting techniques by allowing short deliveries to be comfortably hit in front of square on the leg side. As others have said without a helmet you have to get inside the line which limits you to turning the ball around the corner behind square. This is pretty easy to set a field to - a deep backward square and a fine leg is all you need as protection. Now when bowlers try the short ball tactic they need at least a deep midwicket in addition since pretty much all good batsmen are adept at whacking these deliveries in front of square. In addition there's no need to commit precious reaction time getting back and across so the batsman has their weight forward to play straight bat shots.