Exit polls are all conducted for the four big networks by Voter News Service, the shady organization in New York City. We have parts of two exit polls on videotape, one in Kentucky in 1990, and one in New Hampshire in 1996. Everyone knows that there are very few exit polls. Because hardly anyone has ever seen one, or heard of one, or knows anybody that has ever seen one or heard of one. The late Collier Brothers told me that this confirmed what they found when researching exit polls.
People are busy.
Rushing to work. Rushing from work. Picking up the kids, etc. etc. etc. This is real life. Many people don't have time to stand around and fill out a questionnaire after they vote.