In a nutshell, your video can be perfectly framed, but with bad sound and light it will be less effective. Good sound and light make your videos professional, and make it more likely to be shared by others.
And, remember, sound is half of the information in a video; consider it for every shot. If your sound is unusable, it is possible to remove the sound and replace it with different sound or no sound at all. See also the section below on external equipment.
For more lessons on how to achieve quality sound and light, see this Video for Change guide on how to record quality video on low-cost devices.