The spirit of the law is not just to save third party lives.
When you cause an accident, you drain society’s emergency response resources (and increase the premiums of those in your insurance pool).
35mph vs 30mph is a terrible example - this is the scenario where pedestrians and cyclists are most likely to be around. 75mph vs 70mph would have been a better example.
Driving at night is more dangerous than at day because of the reduced visibility.
Driving when fewer other road users are around is safer than when it’s busy, but you don’t have perfect knowledge and there may be road users you haven’t seen, especially at night.
There’s no objective moral cliff edge between 70mph and 70mph+ε, but there is one between complying with the law and breaking it. Society collectively draws the line somewhere and you don’t get to unilaterally decide everybody else is wrong. I’ve heard people saying “I was only going a little over 30!” called speedo pedos, because it’s exactly like saying “she was only a little underage!”.
Check out the sibling comments for examples of people who thought they knew better but didn’t.
The thing about Scotland is completely wrong, I have no idea why you would think that.