[sdiy] JFET switch question

[JH.]

Hi,

this is a question about using a JFET as an audio switch.

You all know the configuration:
D and S are used as the two switch contacts.
G is used to control the switch. A diode is connected to G (in opposite 
direction as the FET's own gate diode).
Speaking of a n-channel FET like the 2SK30, the anode of this diode goes to 
G. If you connect the cathode of this diode to the negative supply, the 
switch is open. A positive voltage, or even no external voltage at all, 
closes the switch, because the FET conducts.
So far so good.

Now, in most applications we see a high impedance resistor added from G to 
either D or S of the FET.
In some other applications, this resistor is missing, and we find a 
capacitor in the range of 10nF ... 100nF from G to GND.
The latter is obviously intended for smooth transitions rather than for hard 
switching.

Now I wonder: We rarely see this kind of switch without this capacitor and 
without the resistor.
Why is this? For a very simple switch, wouldn't just the FET and the diode 
be enough?
(Obviously no smooth transition without a capacitor - but what's the 
disadvantage compared to the FET + Resistor + Diode solution?)

JH.