I agree with both of the posts above, and would like to add a couple of final points from a more practical perspective.
First, it would be difficult if not impossible in most situations for native peoples to keep and preserve large amounts of meat in that it was labor intensive to preserve it without the benefits of refrigeration/freezing, and the processes they used were not able to handle a large supply of meat at once.
Secondly, hunting by aboriginals in the days before both European contact and technology denied them of something else critical for hunting - guns and horses. The Plains Indians for example numbered around 200,000 even after centuries of existence there, and a large reason for this was that they were not able to hunt and keep enough food to support a larger population than this.
I agree with the above answer but would also add an additional point.
At least in the United States, many people believe that aboriginals (Native Americans or "Indians") killed only what they needed for food because they had an innate respect for nature. It is alleged that they knew that animals had a right to exist and that humans should only kill them when they had to (and should show respect and appreciation as they did so).
A very similar argument is that these aboriginal people were so much more attuned to nature than we are that they knew that overkilling would endanger their ecosystems.
People who believe this portray aboriginal people as much more environmentally conscious than modern people. It is not 100% clear if these beliefs are accurate.
I believe aboriginals here refers to people native to a land and living in forests and depending on gathering and hunting for food. Also, I assume hunting here refers to hunting of animals.
Aboriginals killed or hunted animals only for food because of two reasons. First they had no spare time or energy left, after the the efforts they had to put in just to get enough food to eat and survive. Also, they had no means available to hunt animals on a large scale, or to make hunting easy or safe enough to be enjoyed as a sport. The second reason was that they faced no specific danger from animals, and therefore had no need to kill them from safety. In Forests, animals kill other animals, only for food. Luckily, for humans not many animals considered it worthwhile to hunt humans for food. And eve if some animals did attack or hunt humans, is was safer for them do adopt defensive measures, rather than try to take the offensive route of trying to kill animals that attack them.