I didn't hear anyone mention this so here's my belief why the big three are the big three...
ADVERTISING. When you see a bow advertisement, what companies do see 90% of the time - Matthews, Hoyt, Bowtech, and sometimes Martin. This is what people see and hear the most of therefore, this is what they desire. I have a friend that went out a couple years ago looking for a new bow. I told him to shoot every make/model that he could before deciding. He shot 3 or 4 different bows and settled on the Matthews. A year later I purchased a Buckmaster G2. When he shot my bow, he couldn't believe the difference. When he asked me how much I paid for mine and I told him, he wanted to crawl in a hole and die. He couldn't believe I spent that much less and got a bow that to both him and I (now this is our opinion) was more comfortable, smooth, and shooter friendly.

So kudos to Jennings/Buckmaster/Fred Bear and whoever else belongs to their company - you make a great bow that is affordable.