Do we have to draw resonance structures?? What's even the point?
If you know what the most stable resonance structure is, then good, but it doesn't make drawing resonance structures suddenly unnecessary.
Resonance structures tell us how the electrons are distributed throughout the system.
In order to know how the molecule actually is in real life, we have to know all the major resonance structures, as they all contribute to the resonance hybrid structure.
For example, all these:
add up to become this: