I think most people have brightly colored patio/deck furniture, sunbrellas, and awnings and are looking for rugs that will be complimentary rather than compete with what they already have.
For me, I want the COLOR to be quiet, and the PATTERN to speak (but speak quietly).
If the rugs were done in bright, attention grabbing colors and then patterned, then paired with other furnishings it would suggest too much of a circus atmosphere.