Please RSVP?

A couple paragraphs from Grammar Girl's April 19 e-newsletter:

Last week's newsletter was a disaster! Not only was there a typo (yes, we have a proofreader and review the copy more than once), but also in the section about my New York City book signing on May 1, I wrote "Please RSVP." Oh, the horror! I've known that "please RSVP" is redundant since junior high.

"RSVP" is an initialism of the French phrase "répondez s'il vous plaît," which means "reply if you please." Since "RSVP" already has "please" in it, "please RSVP" is redundant.

Why did I write "please RSVP"? All I can say is that we all have bad days.