There’s a public health reason for that. How many people have ever contracted HIV from a used e-cigarette?
On a different note, as someone who's used e-cigs to wean off cigarettes and eventually quit altogether, this ban is pants-on-head puritanical stupidity.
That's both an amusing mental image and a pretty great idea. One that has no analog with hypodermic needles, so it's still a false comparison.