Why does electronic music have higher fidelity?

Yes, but, in my limited experience of recording, the bass guitar has always been recorded by direct connection to the mixing desk.

There also begs the question, unless you are meaning a synthesiser that has samples, sticking strictly to the meaning of synthesize, what is the sound being faithful to?

Then I add my own question about fidelity, I am old enough to remember the introduction of fuzz box to guitar, essentially an overdriven amp so that a sine wave is clipped and becomes a square wave. With vinyl how does the stylus track this?

I think the "fidelity" depends on the recording not the genre.

But yes, if the music is generated digitally, it is possible for it to be kept intact, avoiding any compression or filtering etc, or even bitrate and depth changes, so it remains as originally played until it reaches a DAC. And if at home you had a DAC, amp and speakers identical to those used in a live performance and in an identical room there would be perfect fidelity, so the main causes of differences are the fidelity of your DAC, amp and speakers and room effects. Compared to that any analogue music source, whether recorded by microphone as with acoustic instruments and voice, or directly from the signal of, say, an electric guitar, is also subject at least to the digitisation process.

But in reality the mastering of a final recording that the customer buys, whether that be a CD or a hi-res file, imposes changes to the sound, and that to me seems to be from where the biggest differences arise.

If you include vinyl in the comparison that imposes its own inherent limitations on top of the aforementioned, which might make additional changes in comparative sound, for example if one recording has a wider dynamic range than another and needs compressing more - though there, potentially, the medium might reduce differences between the originally digital and the originally-analogue musical sources. 

Fidelity usually comes from the quality of gear at the studio/mastering facility.  

Electronic music often follows a trend on what sounds 'hot' set up from those who have the time and inclination to experiment - often from a large enough resource offered from a record label.   Although there's plenty of great material cooked up in bedrooms on home made kit and released on a minor label.

So with a band recorded on a simple device in a garage or someone singing and plucking a cheap guitar sitting on the front porch.

This track was from 1974 yet sounds like the future.

To the OP: higher fidelity? You've obviously never heard early Cabaret Voltaire or Throbbing Gristle then...