Many is the man who has watched with envious wonder as the male dog easily licks its testicles. In an age-old joke, we are posed the question, "Why does a dog lick his testicles?" The answer, of course, was "Because he can!" The joke has, however, been updated with the new punch line, "Because he can't make a fist."
Take dating for instance. Again, like their human counterparts, they also face tough standards and expectations. Some men can only dream of the canine's blatant disregard for monogamous relationships. For all we know, they too have tough standards and expectations to live up to.
Unlike human relationships, dogs are not subjected to the specter of commitment. They are not expected to settle down and tie themselves to one mate and only one mate. For the most part, running the household and parenting is usually left to the distaff member of the union.
Indeed, they are not required to hold down a job to earn money to pay the bills. They aren't expected to go straight home after work. The female doesn't worry about her mate's fidelity. The male doesn't worry about image and is not especially known to show good taste. The sight, and more significantly, the scent of the female has been known to distract him from responsibilites.
After all has been said and done, it is really quite simple why the dog is man's best friend. Ignoring the species, man and dog are actually very much alike!