Postmen's Christmas card (read: tip solicitation) had 3 one-cent stamps. Why bother?

Factual Questions
1

I was doing a little house cleaning when I came across the Christmas card that my postal carriers left in my mailbox around holiday time. I am not on a personal basis with my postal guys – this was one of those little generic cards that they sprinkle in all the mailboxes on their route every year, essentially seeking a tip.

The curious thing about this year’s card was that it came with postage (I don’t think past year’s cards had any stamps). There were three uncancelled one-cent stamps on the envelope. I found this curious. Why three stamps? Surely one or two – or even none – would have done the trick, since the card obviously did not have to go through the real postal system?

Now before anyone tries to answer my post, please keep in mind that I am already aware of the following facts:

  1. It is against postal regulations for postal carriers to solicit and/or accept tips for their services, during the holidays or any other time.

  2. It is illegal to use a USPS mailbox for material other than genuine USPS mail, which these cards probably aren’t.

Okay. So back to my question. Why do you think the guys went to all the trouble of using three stamps?

Thanks all, in advance.

2

He probably wanted a casual observer to assume this was something that legally went through the mail, implying that he had an approved right to a tip.