Here's why:
* Visual: We associate "bubbly" with the visual image of bubbles, whether in a glass of champagne or a bath. The word evokes the round, shimmering shapes and the movement of rising bubbles.
* Sound: While the sound of bubbles popping can be associated with the word, it's not the primary imagery. "Bubbly" focuses more on the visual appearance.
Therefore, even though "bubbly" can have an auditory component, the dominant imagery is visual.