Because of cost. It does seem that Calfee takes the time to develop a rifle more, so that when he turns this over to a customer, it is probably ready to compete at a high level. And time, as they say, is money. It appears to be a good business model, as it seems he has a backlog of customers.
What makes Calfee controversial is, in order to better control the time he has to spend, he limits the components he works with. But instead of saying something like "I know how to make XYZ work," with his teasing prose, he comes close to saying "only XYZ work." He never quite makes the blanket statement, because that would open him up to entirely deserved criticism.
This whole matter of ignition is a laugh for me. We have the same problems in CF. There are 3 basic mechanical ways to improve ignition: (1) increase the spring tension, (2) increase the mass of the firing pin, or (3) increase the length of travel of the firing pin. Each involves compromises. Most effective, it seems is to increase the travel a bit and increase the mass a bit, maintaining good spring tension. Long, long discussion of all this on the 1,000 yard forum a while back. Something like this is what Calfee means by "momentum." But since Calfee seems to be a cult figure, the science gets taken out and the words he uses become things in themselves.
I'm just starting to shoot rimfire. There is no help for beginners on this forum -- or for that matter, most any forum I've seen -- without wading through a ton of junk put out by the pro/anti Calfee people. Hard to talk science when so many want to talk religion.