function Start () {
    var number1 = Random.value;
    var number2 = Random.value;
    Debug.Log (number1 + " " + number2);
}

The only reason to set the seed is if you want a repeating sequence of numbers.

seeds will help you to generate different sequence of numbers. the random functions are not really random and they use an algorithm to do their job. seed is the number that is the input of the random function and will lead to different sequences.

don't change your seed when debugging but when you are sure that the code is working great. then use DateTime.now or ... to make it really random. so with one seed, each time when you call random you will get a different value but in multiple game sessions, you will get always those same random numbers. the sequence of numbers will be the same.