Why even bother with it? Everyone (almost) sells it. Even the Hotels and dollar stores.
Why should I spend even $3 for something I can keep in my travel bag, and takes almost no space and weighs almost nothing?
I keep a small bag of detergent tucked away in a not-often used pocket of my travel bag. I'll wash clothes during extended stays and dry them over the shower bar. Works perfect.
I've never had it asked about or taken, but I assume that's because they just haven't seen it yet.