Because they are 1 of 50 states. A state is a single member of a union. The influence of a state should not be determined by geographic size or population.
The compromise of quantity of electoral votes was in response to your argument. I am saying that it was a poor compromise that has resulted in eroding the protections of the electoral college as populations have grown.
What we have is like saying the fat guy in the group counts a 3 people.