Why is it not possible to come up with a single method of coding pictures that is suitable in all situations?

Because in different encoding methods, the image is stored in different ways, and in different areas it is necessary to encode exactly the method that is more suitable for a specific situation. Somewhere it is necessary for the image to look clear, natural, somewhere it is necessary for the image to scale well.

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.