I can see how "we're in your neighborhood so we thought you might want to use our services while we're here" could work. When I first moved into my house a few years ago, I wasn't familiar with tactics used by door to door salespeople, so I legitimately thought they were in the neighborhood and to save them on a second trip, they were seeing if they could drum up some additional business.

It was only after just about every door-to-door salesman used that excuse that I clued in that he's probably just a sales guy going to random neighborhoods and not actually one of the workers on the ground doing the job. Anyway, my point is most people don't think about these things, and especially not new homeowners, and probably just take their word.

Regarding the $10/window guy: I've been meaning to get out the ladder and clean all my windows myself but have been lazy, so if somebody actually showed up at my door, quoted a price, and said they'd do it right then and there, I might take them up on the offer. It's really just a numbers game for them.