While steak lovers enjoy a range of doneness—from the barely warm “blue” to the thoroughly cooked “well done”—chicken doesn’t offer such flexibility.
Online discussions have pointed out that when it comes to poultry, rare isn’t an option. And there’s a very good reason for that.

Restaurants and home cooks alike avoid serving undercooked chicken not out of culinary snobbery, but out of concern for your health—and legal liability. As the US Centers for Disease Control and Prevention (CDC) warns:
“When cooked, chicken can be a nutritious choice, but raw chicken can be contaminated with Campylobacter, Salmonella, or Clostridium perfringens germs. If you eat undercooked chicken, you can get a foodborne illness, also called food poisoning. You can also get sick if you eat other foods or beverages that are contaminated by raw chicken or its juices.”

Beef steak, on the other hand, is typically made from single cuts of muscle. This structure means that any bacteria introduced during processing usually remain on the surface. A quick sear at high heat can kill those pathogens, making it safe to eat the interior rare.
Chicken differs in both texture and structure. Its porous nature allows bacteria to penetrate deeper into the meat, making surface-level cooking insufficient. To ensure safety, chicken must be cooked thoroughly throughout. So unless you’re oddly fond of gastrointestinal distress, that medium-rare chicken burger should stay off your plate.

Source: iflscience.com