Many of them are indeed fat. Just look at that Ruiz guy, he still had some baby fat on him. Even Chris Arreola was fat until he re-dedicated himself to physical conditioning. There are also heavyweights in the past who looked or were really fat such as Buster Mathis, Tony Tubbs, Tim Witherspoon.
The short answer is that they lack the Discipline of the Klitschkos.
.
Both Vitali and Wladimir are very proud boxers. If either ever loses a fight again before they retire, you can be sure it won't be due to lack of preparation.
.
Both Klitschko brothers are very proud gym rats. Most boxers fight for a quick buck. While they certainly would not fight for free, you can clearly see that the Klitschkos take their craft seriously.
It's just who they are.
Boxers eat a hole bunch of fat foods I mean all kinds of fat foods because fat turns into muscle same way with bodybuilders
I'm curious why so many light-heavy and heavyweight boxers look fat. I thought cardio was super important for boxing (even more so than MMA), and I know they have strength (knockout power) so why are they fat? Why don't they trim that and ripped, wouldn't that be better for dodging?