We associate it with photos taken quickly, no time for the craft of arrangement or perhaps even consideration for aesthetics. The point is to capture something before it gets away.
Verbal snapshots perform the same function.
They aren't meant to be pretty crafted texts. They might exhibit moments of grace, but accidentally, not as the result of painstaking effort. The point is to capture an idea. Ideas are slippery. They can get away while we're diddling with craft.