There are a few practical challenges. These include:
It can take up to 28 days for poisoning symptoms to become visible in the human body, making it difficult to pinpoint the source of your illness and prove who is responsible.
The plaintiff has to prove that the food they ate was contaminated, and that it came from the restaurant and caused their illness.
Foodborne illness cases are seldom severe enough to justify investing the time and cost to fight a lawsuit, not making it worth your while to pursue the case.