Hot dogs that are made from chicken, pork etc are already cooked and can be eaten cold and straight out of the package.
But it's recommended to heat the hot dogs up at least before eating them to kill any potential bacteria that could be on the hot dogs.
I used to eat hot dogs straight out of the package in the store with my mom shopping as she would hand me a hot dog to eat to keep me occupied and keep me from being hungry.
I will sometimes eat hot dogs without heating them up or cooking them when I am hungry and just want a quick snack to tie me over until I cook something.
However I prefer to heat the hot dogs up first even if I pop the hot dog in the microwave for 30 seconds or so to heat it up.
Warm or hot hot dogs are more tasty than cold hot dogs.