I found my Sony straps to literally cut into my flesh, especially so when carrying the complete thing: the body + the vertical grip with 2 batteries + the Zeiss lens. That makes up for about 3.8 kilos.
The Hasselblad I had the pleasure of playing with a couple of years ago weighed in at 5 kilos. I wouldn't like to carry that thing around all day without some way of distributing the weight. But it might be my posture --I'm a VSP, a very skinny person