There's a long list of possible reasons for differences in maker warranty policy, but one is simply a numbers game. Assuming all things equal, the gross numbers of failures will mirror success in the market place. So a company with fewer CF frames out there won't see many failures and can more easily rationalize the cost of those few replacements as a marketing expense.

With more bikes and more failures, replacement cost is significant, so a larger company may (only a possibility) feel that they need to look closer and separate true defects from those failing from outside causes. This would be especially true if their sales are skewed to an audience that rides more, so the rate of failure is higher. After all bikes don't fail while sitting in garages collecting dust.

Personally, I have a bias toward metal frames, reflecting the fact that I work in metals and understand them better. But in fairness, I'm not sure that CF frames are more dangerous. They only seem to be, because they're under a microscope, and have a larger share among riders that ride more.