Bee Stings Are A Crappy Standard For "Painless"

How did it come about that bee stings mean "painless"?
When I ask someone if something (an injection, a procedure, a test, a needle biopsy, a piercing, etc.) will hurt, they say,

"Naw... it won't hurt. It will feel just like a bee sting."

Well, the last time I got stung by a bee, it hurt a lot.
The bee flew into the tiny space in between the arch of my foot and my sandal, mid-step. As it happened, I was already stepping down as I felt a furry buzzing, and it was too late to change course. I was stung immediately and my foot felt like it was on fire. Though I removed the stinger properly and soaked my foot in ice water mixed with baking soda, then applied meat tenderizer with vaseline, it hurt like mad and throbbed the rest of the day.

How can anyone say that experience is painless, or even nearly so?
And why do we allow them to hold up that kind of experience as a comparison for how something won't hurt?