STAGGERED START: The Southern League begins a week later

I KNOW it’s been asked time and time before but can someone give me a reasonable explanation as to why the Southern League start the season one week later than everyone else?
Don’t get me wrong, I’m not suggesting that an August 12 kick-off is either too early or too late – in fact it’s about right – but I don’t understand why all three Step 3/4 leagues can’t start at the same time as the National League.
I find it odd also that all three leagues still finish on the same day as the to...