One cool thing about multimodality is that it can attend to multiple senses, which is sometimes necessary ii a reader has a preference or need for one mode of communication over another
This is another compelling reason to add multiple modes to your work. Although quality in a work is important, quantity is important as well. The larger the audience that you work can reach, the more likely it is to accomplish its goal. If certain people can't access your work, whether it is because it lacks visual modes and the person is deaf or auditory modes and the person is blind, then you are automatically eliminating the chance that your work will have the desired effect upon them.