Water Salesmen scam?

While we are on the subject of scams, has anybody had water salesmen to door to door? I’m so confused what the end game is for these people. I have a sink and a Brita filter. They’re very aggressive and I don’t even know how to react to someone selling me water aggressively. I had this girl almost barge into my apartment the other day to get me to buy water.

She asked me where I get my water? Literally everywhere. I shower in the stuff every day? What are these people actually providing me? What’s their goal? Why would I give them money for something I already have? Can someone please explain this industry to me?