Clarity

Another reason you might want to use this is for code clarity.

It is a lot easier to know that a particular line refers to a field or method on the same class if there is an explicit this. before the reference.¹

class Elmo {
    int age;

    void sayHello() {
        System.out.println("Hi, I'm Elmo");
        System.out.print("I am ");
        System.out.print(this.age);
        System.out.println(" years old.");
    }
}

void main() {
    Elmo elmo = new Elmo();
    elmo.age = 3;

    elmo.sayHello();
}