Speaking is normal. In fact, it is so normal that it is automatic. If you take young children before they speak and separate them from adults they will invent their own language. It is well known that identical twins often invent their own language.
Speaking a language is so typically human that one never finds groups of humans without language. They’ll invent one, if necessary. That’s why we have pidgins and creoles.
But reading is not normal. Put a bunch of children together without a teacher and they won’t learn to read all by themselves. In fact, some human societies existed for thousands of years without inventing reading and writing. They are not less human for that. There is nothing innately human about reading and writing. No matter how long we have schools, children won’t start learning to read on their own. Every child in every generation has to learn the skill. It’s not natural, not spontaneous.
Even though Europe had reading and writing for a very long time, it is only recently that it has been widely practiced. You probably wouldn’t have been able to read this had you been born at another time in history.
But today most of us take reading and writing for granted. It is so much a part of our lives that we think that it is normal. But for many marginalized and bibleless peoples, not reading and writing is normal and reading is the exception.