Button and resistance

Although I’ll kill you, I don’t understand why the button needs to be connected in this way:



Why can not I connect the button in the same way as the LED - in series with the resistance? I tried it. The effect is completely opposite. The simplest sketch “the button is pressed - the lamp is lit” acts exactly the opposite - until nothing is pressed, the LED flickers (and does not light up evenly!). Press the button - the diode goes off.

#define BUTTON 7
#define LED 12
int btnState;
int btnPrevState;
void setup () {
  pinMode (LED, OUTPUT);
  pinMode (BUTTON, INPUT);
}
void loop () {
  btnState = digitalRead (BUTTON);
  if (btnState == HIGH) {
    digitalWrite (LED, HIGH);
  } else {
    digitalWrite (LED, LOW);
  }
  delay (10);
}