As I mentioned above, it's one of the two major functions in hypnotism: delivering suggestive material to elude critical thinking. When someone asks you a harmless question, we don't tend to ask ourselves whether he/she is lying. However, here, we introduce a benchmark for any further opinions that the brain needs to check against - which serves as an effective suggestion.

You'll see similar suggestions through tone changes (down for commands when asking questions for example), and stories. It's quite fascinating!