Several factors come to mind:
1) They work harder, more labour-intensive jobs, for longer hours.
2) Less preoccupied with their appearance (which is a less-significant factor in overall attractiveness, compared to women), and so may shower less frequently or more carelessly
3) Spend significantly less on perfumes and cosmetics, which mask odours
These would explain your observation, but your observation in faulty and clearly ignorant:
1) Women also poop
2) Women also fart
3) Women also sweat, but I admit it is somewhat reasonable to conjecture that men sweat more (owing to more physical exertion as above, but also having to physically move more weight and regulate a physically larger body)
4) You've neglected some obvious contradictions to your premise, as you simply assume women are the cleaner and gentler sex, and thus evidence your ignorance. Two of the most notable exceptions are 1) Women menstruate for approximately 2 days every month. This is unwanted discharged which must be collected and removed throughout the process (i.e. cleaned). That is to say, dirty. 2) Besides menstruation, women regularly produce vaginal discharge. A woman buys new underwear because all her old pairs are grotty. A man buys new boxers because his old pair have become worn and tattered. This is also, perhaps more obviously, dirty. A penis is much easier to keep clean than a vagina.
5) Men are hairier which may prejudice people to think they look dirtier than they really are.
