Why do they say Floyd mayweather has no power in his punches?

now im not by any means saying Floyd is a power puncher or even a strong puncher but i usually hear from manny fans that the pac-man will just shrug off his punches... do they not realize that floyd may not have a 1 punch ko type power but the shots he does give you add up over the coarse of the fight which is why he has a 60% knock out ratio.