The reason why diner burgers taste different is mainly because diners use hamburger meat that has a high fat content of 80/20 meat blends.
Diners also use a seasoned flat top griddle as well as high heat cooking techniques to create a nice savory crust.
The diner burgers also often feature freshly ground beef as well as the use of specialized seasoning and toasting the hamburger buns in butter or even beef tallow, which provides a richer and more indulgent flavor when compared to the home cooked burgers.
Cooking on a griddle that is seasoned, allows the fat from the other burgers that were previously cooked to also baste the current burgers being cooked, which adds a deep and savory flavor.
Chefs in diners also heavily season the hamburger patty using salt and pepper just before they cook the burger.
Diners and restaurants often use beef that has at least 20 to 30 percent of fat, which remains juicier, more tender and also provides a stronger and richer flavor.
And instead of using standard ground beef, many diners and restaurants also use a mix of cuts of meat like chuck, brisket or short rib to get a superior taste and texture.
Also many diners and restaurants also smash the hamburger patty on the hot surface of the griddle, which creates a Maillard reaction, which is a chemical reaction between the amino acids and reducing sugars, which helps produce a crispy and caramelized crust while also locking the juices into the meat.
And using butter or even animal fat like Tallow on the griddle and on the hamburger buns also add some extra layers of flavor and indulgents.
Diners also often will use fresh and soft and toasted hamburger buns, which is combined with precise and simple toppings for the burgers to enhance instead of overpower the hamburger meat.
To make your burgers at home taste better you can also add herbs, cheese or Worcestershire sauce.
You can also add some Jalapeno peppers to your burger or hot sauce and or add some toppings like fried eggs, chips, bacon, bacon jam, sauteed onions, sauteed mushrooms, caramelized onions, avocados, blue cheese or even grilled pineapple.
Some other good sauces to add to your burger are truffle aioli, sriracha may, aioli, chipotle mayo and you can also toast the bun or use different breads.
Crispy bacon, tangy pickles, garlic butter, rosemary, thyme herbs, BBQ sauce, cheddar cheese, feta cheese, cream cheese pepperjack cheese and even garlic can all help to pimp your burger and make the burger more enjoyable.