I agree that there is an NA attraction to smaller cartridges for hunting and I agree that you are not at a disadvantage with "more" power... if I may extrapolate and extend the logic, I will take exception with the notion that a sufficient cartridge is a "disadvantage" over a "greater" cartridge... A properly placed bullet with a "sufficient" cartridge will kill as cleanly as a "more than" sufficient cartridge... as always it is the hunters responsibility to stay within the limits of his/her cartridge choice and properly place the bullet... one is not being "foolish" in choosing a .270, 7X57, .308 or .30/06 (well maybe the .270

) to hunt moose, over say, a .300 WM, .338 WM, .375H&H etc...
Challenging oneself is not "ego." I don't give a "ratz azz" how I am looked upon as a hunter... I do care how I feel as a hunter. As a newbie 15 year old deer hunter, I was placed in the sweet spot by our deer hunting party, and on opening morning of my first deer hunt, I shot five deer in under five minutes with my grandfathers tired old .32 Special... it was an exhilarating and highly charged moment, which I remember fondly... all the back slapping and retelling of the tale and the liver and onions that night... but in the days that followed, I began to feel a letdown, like I had missed out on something important in the experience... I had started bowhunting a number of years earlier for non-game species and decided to give bowhunting a "go..." the next fall I arrowed my first big game animal, a black bear, at under five FEET, stalked while feeding on acorns... this started a 40 year love affair with bowhunting, that continues with as much passion today as it did forty years ago... This was not "EGO," this was maximizing the experience, bowhunting forced me to slow down, become more in tune with my surroundings, more knowledgeable about my quarry and its habits and habitat... I learned to stalk within bow range of wild big game animals, to use their own vocalizations and feeding/movement patterns to my advantage, and in doing so, I found the elements that I had missed during that first adrenaline filled experience with grandpa's .32 Spl. If archery gear had not proven itself to be rapidly lethal in harvesting game, I would have abandoned it long ago... the truth is, as any studied bowhunter can attest to, archery gear is as EQUALLY lethal as any cartridge you might choose to hunt with... it just comes with a number of additional elements (handicaps) that must be observed... rather than a 400 yard shot on a bull moose with a .300 WM (or, or, or...) I take a 20 yard shot with a 70 pound bow and broadhead tipped arrow, rather than obliterating the shoulder on a quartering on bull with a .375 H&H, I must wait for a broadside or quartering away posture to open up the lung area to receive my arrow... these are restrictions that I gladly accept, and when circumstances are not right, I let the animal walk and admire the moment... I have been within touching distance of trophy big game animals and never loosed an arrow, such is the nature of the game, and the reason I love it so much... EGO has nothing to do with it...
5) Because it is unnecessary to get the job properly done... "Over"kill is not necessary, "kill" is necessary. Have enough cartridge/bow, practice to become profficient, stay within its limits, take an appropriate shot at and appropriate range, and perform well at the moment of truth... fire up the BBQ.