Because, honestly, we've been here for hours.
When the meeting has devolved into an endless discussion of someone's cousin's cat's health issues, it's time to make a break for it.
Slide-their-hands and make a run for it or Pretend-to-care and just quietly gather your things.
Either way, you'll be free to Pretend-You-Never-Were and avoid the inevitable Awkward-Goodbyes.