I was talking to a leather strap maker about some custom straps. But why 3" wide, he asked. Well, because I'm a bass player yada yada yada. It's known bassists like wider straps especially for longer gigs.
He gave me a different take - one that he heard directly from Keith Richards. Keith asked him for a very skinny strap, and this guy didn't have anything skinnier than 2.5" at the time. Because, weight, right? Keith basically told him (starting with 'oh, you're gonna tell me about guitar straps, mate?'

). An ergonomics lesson from Keith ensued. He first had him wear his guitar (which had a very skinny strap already). Now act like you're playing and look over your right shoulder for a cue from the other side of the stage. Now raise your left hand and act like you're waving to the crowd. And notice when you do, the headstock of the guitar didn't move at all and never needed to be re-adjusted.
With a wider strap the guitar is always moving.
He went on to describe how he also realized that (he believes) there is less fatigue on a skinny section of your shoulder instead of weighing down your whole trapezius muscle and pulling on your deltoids, and in the opposite direction your neck, in the process.
And he said think about it because his clients learned from the old guitar slingers like Jimmy Page who used 13 pound Les Pauls and had the skinniest straps. I thought it was all for looks.... Made me think of Dug Pinnick too.
I still went with the 3". I have a bunch of LK's and they are 3.5" which feels great to me. But I never considered how the bass does tend to work it's way over towards me deltoids and that is when I feel the weight of the bass most.
Most of my basses are around 8 pounds anyway.