Downs in American Football make a huge difference too. Teams have 3/4 tries to go a total of 10 yards. A yard on a running play is very important so running fu

Downs in American Football make a huge difference too. Teams have 3/4 tries to go a total of 10 yards. A yard on a running play is very important so running full blast into someone to gain/prevent an extra yard is worth it. In Rugby, it doesn't really matter if you go 3 or 4 yards before being tackled.