Some people like to do this but it's bad mic technique and really amplifies background noise. Most of the time you'll sound better talking a few inches from the mic and just turning the mic up just enough to reach 100% modulation.
The d104 is a high impedance mic element and sounds best when connected to a high impedance input. If you connect an unamplified d104 to a modern radio designed for a 600 ohm mic the low frequency response gets chopped off. I'm sure you've heard someone say d104 microphones sounds tinny. They can if you use them wrong or buy one with a bad element.
The amplifier board in the base not only amplifies the audio but gives the element a higher impedance to work into. The factory components in the amplifier board are still restrictive for some taste so people started building their own amplifier boards with fets. A friend of mine makes up a batch of boards and sells them when he has time. They work great with a good d104 element and modern cb set. Unfortunately many of those old elements are dried out junk so buyer beware of those shiny silver eagles. The latest craze is replacing the d104 element with a condenser element. Some of them sound very good but it's not a d104 anymore.