That's the social control function of the Law of Homicide. Intention is something harbored in the mind before the act is done. One can always reflect on their intentions, and change their intentions before harm is done. The difference between risk and intent is that risk exists in the real world while intent exists in the minds of actors. Intent, considered as a mental construct, can also include unrealized intentions .
Trespass becomes burglary, for example, when there's intent to commit a felony therein.
Intoxication bears an interesting relationship to Intent. Even voluntary intoxication might be an excuse or justification. The general rule, however, is that intoxication negates a specific intent, but not the general intent. General intent is the intent required for the base crime, and specific intent is the factor that aggravates the offense. An intoxication defense might mitigate a homicide to a manslaughter, but it can't generate an excuse for the felony of murder.