It's important to have some sort of fail safe mechanism whether a fuse wire, fuse or circuit breaker inline between the battery and the voltage regulator.
Else you can unsuspectingly experience a experience a dead short, melted wiring or even watching your bike go up in flames (literally).

Horn brackets that are mounted along with the key switch between the cylinders has been known to cause meltdowns.
The fact of the bracket breaking (due to being loose, vibration, age etc,) isn't the problem.
The key switch terminals are bare ended (no insulation).
Should the horn bracket break, the horn will (most likely) swing down & rest on the back of the ignition switch for awhile, shorting the terminals.
The subsequent dead short heats up the wires, melting them and triggers the carnage shown below.
At this point, the motor is dead, no lights, no nothing. You're stranded on the side of the road, wondering just what happened.

This happened to a 74 XLH:
This particular bike did not come with a fuse wire installed from the factory. So the main circuit was unprotected. \\
See the 'before' pic of the horn / switch brackets below (taken ≈ 8 months prior to my catastrophic event).
The ends of the ignition switch wires were heat-shrink'd immediately after this pic was taken.
Note the exposed screws on the back of the ignition switch.

Next, the meltdown occurs. I phone my son to bring tools, wire, etc etc. I re-wire enough of the bike, while on the side of the road, to get me home.

For the fix, I added a reinforcement to the horn bracket & TIG welded it up, replaced all those wires, & added my own fuse wire.

Before pic. Note the relative pristine condition of the horn mounting bracket, p/n 69129-72. ¹⁾

After pics. Back in the garage, with pics of the horn mounting bracket, et al, after removal. ²⁾

First pic below is the RED wire from the solenoid to voltage regulator, note the insulation (on what was the RED wire) has evaporated.
On a '74 XLH, this wire is the main feed that runs from the solenoid to the Delco voltage regulator.
I fully expected this wire to be burnt thru. It wasn't. Another RED wire burnt thru first, otherwise I'm certain it would have burnt thru.
The outer black sheath is mostly in tact.
The second pic shows the wire with the outer sheath removed. Insulation jacket was totally smoked, end to end.

Below is what was left of the RED ignition switch wire (about 12 inches was damaged and/or evaporated), which runs from the voltage regulator to ignition switch.
The WHITE wire (feeds the accessory & ignition circuit breakers) and the GREEN wire (feeds lighting circuit breaker) were intact.
(although still damaged due to heat on RED wire)

The outer black sheath housing the RED, WHITE & GREEN wires is mostly in tact except for the damaged 12 inches at the end.
(which had been discarded by the time I took this pic)
Note the RED wire has all the insulation evaporated / melted off in the second pic below. The heat-shrink I installed 8 months earlier is more or less intact.

Here is the black sheath that houses the RED, WHITE, & GREEN wires running along the backbone of the frame.
The wires inside are “crispy & damaged to various degrees” but not burnt thru in this area.