When we assert our body part, we use the method equalTo() but while asserting for Header, we are just providing ("Key","value") pair only. Why can't we use just- body("scope","APP") Any specific reason behind this?

Below is the actual code.

assertThat()
  .statusCode(200)
  .body("scope",equalTo("APP"))
  .header("Server","Apache/2.4.18 (Ubuntu)");