There aren't more speakers of Comanche because the U.S. government has made a practice out of destroying culture, language of indigenous peoples. Less than 1% of Comanches can speak Comanche.
I was fortunate to have a great grandmother and grandmother to teach me....although, they were against teaching me because of what they had to endure in the government boarding schools. I finally persuaded them to teach me more, I had grown up hearing it spoken but never really learned how to speak Comanche, until I was about 8 years old.
I still don't know every word or how to pronounce certain words but can carry on a fluent conversation with someone who speaks Comanche.