Hurricanes last longer. Actually, the list is pretty comprehensive. Tornadoes are very short-lived. To try and name them would be almost impossible. Think about the list of names we'd have to have.
Hurricanes happen much less frequently and they last longer.
Also, there may sometimes be two or more hurricanes happening at the same time. So, name recognition is important to let people know which storm the TV weather people are talking about. But, some tornadoes have actually been named. In these cases, tornadoes or tornado outbreaks become known for their date of occurrence, place of occurrence, or some other key attribute of the event. Thank goodness there are relatively few of these significant events compared to the total number of tornadoes that occur each year.