Why can't I see balloon/confetti animations in my Messages app?

Why can't I see balloon/confetti/laser/fireworks/shooting star effects on my iPhone?

iOS 10 Failed Messages

If you have been receiving messages on your iPhone like the image posted above, then somebody has been trying to send you iMessage animations. Apple introduced the ability to send animated celebration effects through the Messages app in iOS 10. An iPhone users can send animated images of balloons, confetti, fireworks and more to other iPhone and iPad users running iOS 10 or later. If you do not see the animated messages then your device is probably running an earlier version of iOS, or your device does not support iOS 10. You can see a list of iOS 10 supported devices here, and learn how to update to iOS 10 here.

Once your device has been updated to iOS 10 or later you will be able to receive and send animated messages.

Update: It has also been discovered that enabling the Reduce Motion slider in the Accessibility settings will disable bubble and screen effects on your device. You will still be able to send screen effects by typing certain key words but you will not be able to see them or send them manually if the Reduce Motion slider is activated.