>>85817676It was canon though, and that's not the reason.
The laser beam wasn't that special. It was even stated in the movie that Goku sometimes let down his guard.
In dragon ball, all the main fighters are ki based. They can make their fists/bodies harder/more resilient.
Goku just dropped his guard. A bullet probably could kill him in that state (it would move to slow for him not to notice).
