Though annuals complete their life cycle in one growing season, some gardeners prefer their longer and sometimes more abundant blooming period. They can be grown easily in containers and baskets, an advantage to those short on land. Another point made in a forum I found is that a gardener can plant different flowers in different places from year to year, with ease.
I recently received a comment by a gardener who called herself "lazy" because of her leaning toward perennials, which live for more than a year and therefore do not require replanting. If you don't plant your flowers from seed, perennials can be cheaper in the long run for that reason, though they are more expensive than annuals when first purchased. Perennials can also be divided to give to friends and plant in other places. As one commenter in the forum stated, "It's like having a garden centre in your own yard."
Many gardeners like the challenge of growing the right combination of perennials so there is always something in bloom throughout the season. These folks may not only regard annuals as "too easy," but find some of their gaudy colors unnatural in fitting with the native landscape.
Which do you prefer? I think that many people prefer a combination of the two types. If they are like me, they have a few favorite annuals, like zinnias and nasturtiums, and might throw a few others in a garden if nothing else is in bloom. But in times of laziness there is still something that will come up.