Ya mean that dollar I got is not a way of speaking?

My dollars have grown legs too running around the house screaming "NO!!! Please don't get rid of me!! I PROMISE I'll be good, please save me from the Circulatory Firing Squad!!" I just simply say "Shut your green pie hole, I have Bills to pay!"

That conversation happens all the time.

only to be used to pay for things and services. It is not protected speech.

"Whoever mutilates, cuts, defaces, disfigures, or perforates, or
unites or cements together, or does any other thing to any bank
bill, draft, note, or other evidence of debt issued by any national
banking association, or Federal Reserve bank, or the Federal
Reserve System, with intent to render such bank bill, draft, note,
or other evidence of debt unfit to be reissued, shall be fined
under this title or imprisoned not more than six months, or both."

A little writing is one thing, but those stamps cover a vast portion of the face, thus making it (probably) unfit for circulation.

That's why "Where's George" no longer sells the rubber stamps for their gimmick - the heat was intense from the mint.

One must note that paper money don't go as much out in circulation, they are stuck in banks and are moved around through electronic means.

Another thing one must consider, which is out of topic is that there is a recent study that shows that people are more likely to cheat when they put more and more layers behind actual handling of money.

Meaning, people are more likely to cheat, gamble and do crazy things with money when it is substituted as something else. Like a check, card, credits, numbers on stocks and so forth. Which goes a long way to explain why Wallstreet is so crazy.