In the US, those schools would probably be outliers at the high and low end of the spectrum.
a. A small number of elite high schools who design courses that they see as better than AP or IB courses.
b. A probably larger number of poor quality high schools where student demand and ability to succeed in AP or IB courses is so rare that it is not worth offering them.
The middle range to good high schools (and some elites not in category (a) above) take AP or IB courses and curricula because it is convenient to do so in order to offer something for their more advanced students. Most of them probably would not be able to design their own advanced courses any better than AP or IB courses.