I was born outside the US and we had local gangsters that would walk up to you in the middle of the street and try to “sell” you a brick. Like a brick that you build a house or wall with. They would show it to you, and tell you that it was a great brick and that you should buy it. If you told them you didn’t want the brick, they would assure you that yes you most certainly do want the brick. You then bought the brick from them. You can probably image what the brick was used for if you refused to purchase it.

I'm not familiar with this situation, but I'm assuming that whoever is doing this isn't there to "clean" your windshield, and that the entire "transaction" is imbued with the implicit threat of violence and intimidation. You're essentially being robbed through other means. If this isn't the case, then I'm happy to admit that I'm wrong, but that's how it reads to me.