You can learn English from a book, but can you use the knowledge in the real world?
Speaking skills involve not just memorizing rules or knowing information, it is also a practical skill requiring action, similar to playing a sport or musical instrument. Students need motivation to practice.
Many students will learn English but will still have communication problems when using their knowledge. Having the knowledge is different than being able to use it. English is not like history or math. Just learning and memorizing the knowledge is not enough. For example, it is not math. In math, once you memorize 2+2=4 then you can easily use this knowledge. Learning the English grammar rules is not enough, and it is impossible to memorize every English conversation. Situations will be different and making unique conversations will be required. Also, body movement is required for pronunciation, and this physical action is necessary for verbal communication. Learning to speak English is a skill and requires practice. You can read a book about basketball or study the correct way to shoot the ball, but you will not be successful until you practice. Speaking English is also a skill that requires practice.
Unlike writing, speaking requires fast thinking. You do not have time to carefully plan every thought, because communication moves quickly.
The goal of learning a language is to communicate, so focus on your thoughts and ideas. You do not think about grammar rules when speaking your native language, instead you focus on your thoughts. When you are speaking, you don’t have time to think about grammar, and you must focus on effective communication. Did I communicate my thoughts and ideas?