2 straps is the modern way man.
As I'm always late it's better to double strap as you can walk faster than if you're holding one of them.
Aye, I agree in that sense. However, for the real, laid-back, cool look. One strap is the way to go.
You can't single strap when you're on a skate board either.
Practicality isn't cool man. It's rigid, sensible and boring...
What works for Sheldon Cooper and Leonard Hofstader works for me!!