RSVP, respond if you please, please respond

Wikipedia says,

RSVP may refer to:

Répondez s'il vous plaît", a French phrase that translates to "please respond" and word for word means "respond if you please"[1]. It is with this meaning that invitation cards and similar documents are often marked with "RSVP." It is standard practice to reply to an RSVP request whether confirming attendance or declining.

Sometimes, there are people who forget the last part, and, they tend not to reply when they are not attending the event. I just finished talking to a friend whose event will happen in less than half a month's time and yet there's around 25% of the guest list who have not confirmed their attendance yet. She said she's already having a headache because there are a lot of things that affect the silence of that quarter portion of the invited guests. She mentioned some, like the seating arrangement, the number of plates she will let the caterer prepare and some other personal plans she has for t he event.

When you are given an invite which has the letters R-S-V-P printed, are you courteous enough to call and confirm whether you are coming or not?