Why are most telescopes, both for scientific and educational purposes, reflector telescopes, not refractors?

Reflector telescopes have a number of advantages over refractors: one optical surface at the objective, lower (mainly thermal) requirements for glass, and no chromatic aberration. Refractors are mainly used in astrometry because they lack spherical aberration.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.