The activity diagrams become exceptionally large when we are unable to have line wrapping (or multi-line support) in the names of the bubbles. As a result, the bubbles can become greatly broad and squat, hindering readability. See the following link for an example:
https://photos.google.com/search/_tra_/photo/AF1QipPmAIDbVJeYNJvgYpVp6LZKNtlWfw_ySZ2AexM8