StateパターンでStateクラスを作る意味とは

マーチン・ファウラー氏の「リファクタリング」の本を読んでいるのですが、Stateパターンを使ってリファクタリングする例が載っていました。
それをふまえて自分でも考えてみたのですが、なぜ親クラスと子クラスの間にStateクラスを作るのか、その意義がぴんときていません。

例えばPythonの場合、gitHubに載っていたコードでは、継承関係は Radio - State - AMState/FMState となっています。

Python
1""" http://ginstrom.com/scribbles/2007/10/08/design-patterns-python-style/"""
2
3
4class State(object):
5    """Base state. This is to share functionality"""
6
7    def scan(self):
8        """Scan the dial to the next station"""
9        self.pos += 1
10        if self.pos == len(self.stations):
11            self.pos = 0
12        print("Scanning... Station is", self.stations[self.pos], self.name)
13
14
15class AmState(State):
16    def __init__(self, radio):
17        self.radio = radio
18        self.stations = ["1250", "1380", "1510"]
19        self.pos = 0
20        self.name = "AM"
21
22    def toggle_amfm(self):
23        print("Switching to FM")
24        self.radio.state = self.radio.fmstate
25
26
27class FmState(State):
28    def __init__(self, radio):
29        self.radio = radio
30        self.stations = ["81.3", "89.1", "103.9"]
31        self.pos = 0
32        self.name = "FM"
33
34    def toggle_amfm(self):
35        print("Switching to AM")
36        self.radio.state = self.radio.amstate
37
38class Radio(object):
39    """A radio. It has a scan button, and an AM/FM toggle switch"""
40    def __init__(self):
41        """We have an AM state and an FM state"""
42        self.amstate = AmState(self)
43        self.fmstate = FmState(self)
44        self.state = self.amstate
45
46    def toggle_amfm(self):
47        self.state.toggle_amfm()
48
49    def scan(self):
50        self.state.scan()
51
52# Test our radio out
53if __name__ == '__main__':
54    radio = Radio()
55    actions = [radio.scan] * 2 + [radio.toggle_amfm] + [radio.scan] * 2
56    actions *= 2
57
58    for action in actions:
59        action()

これを以下のように書き換えても、全く同じように動作しました。
クラスの継承関係を、Radio - AMState/FMStateというように、Stateを挟まない形に変えたものです。

Python
1class Radio(object):
2    """A radio. It has a scan button, and an AM/FM toggle switch"""
3    def __init__(self):
4        """We have an AM state and an FM state"""
5        self.amstate = AmState(self)
6        self.fmstate = FmState(self)
7        self.state = self.amstate
8
9    def toggle_amfm(self):
10        self.state.toggle_amfm()
11
12    def scan(self):
13        self.state.scan()
14
15
16class AmState(Radio):
17    def __init__(self, radio):
18        self.radio = radio
19        self.stations = ["1250", "1380", "1510"]
20        self.pos = 0
21        self.name = "AM"
22
23    def toggle_amfm(self):
24        print("Switching to FM")
25        self.radio.state = self.radio.fmstate
26
27    def scan(self):
28        """Scan the dial to the next station"""
29        self.pos += 1
30        if self.pos == len(self.stations):
31            self.pos = 0
32        print("Scanning... Station is", self.stations[self.pos], self.name)
33
34
35class FmState(Radio):
36    def __init__(self, radio):
37        self.radio = radio
38        self.stations = ["81.3", "89.1", "103.9"]
39        self.pos = 0
40        self.name = "FM"
41
42    def toggle_amfm(self):
43        print("Switching to AM")
44        self.radio.state = self.radio.amstate
45
46    def scan(self):
47        """Scan the dial to the next station"""
48        self.pos += 1
49        if self.pos == len(self.stations):
50            self.pos = 0
51        print("Scanning... Station is", self.stations[self.pos], self.name)
52
53# Test our radio out
54if __name__ == '__main__':
55    radio = Radio()
56    actions = [radio.scan] * 2 + [radio.toggle_amfm] + [radio.scan] * 2
57    actions *= 2
58
59    for action in actions:
60        action()