why don't i get better resolution when i pwm?

pwm_sketch.ino

#define PWM_PIN 2

#define BIT_RESOLUTION_READ 12
#define BIT_RESOLUTION_WRITE 12

void setup() {
  pinMode(PWM_PIN, OUTPUT);
  analogWriteResolution(BIT_RESOLUTION_WRITE);
  analogReadResolution(BIT_RESOLUTION_READ);
  Serial.begin(9600);
}

void loop() {
  for (int i = 0; i <= 16; i++) {
    analogWrite(PWM_PIN, i);
    Serial.println(i);
    delay(400);
  }
}