Is the coupling there so it doesn't leak?

probably, you wouldn't want to waste any electrons due to leaky pipes

Looks like the zig-zaggy run is also part of the scheme -- It makes the electrons slow down to go through that coupling!

It looks like the original installation was shy on support for the EMT with only one clamp (now uunused) on the booth itself but nothing within 3' of the other end. EMT was (according to what we see now) a poor choice. Rather than replace the damaged conduit or even bend it back into a semblance of its original shape, and, because the original fitting would no longer span the joint, the hose and clamping solution is a poor substitute.

As I look at the damage to the conduit, I would say that this conduit was hit by a car bumper. So would IMC even held up? IMC encased in 2" of concrete across the sidewalk or even properly saw cut into and buried under the sidewalk still would not of held up to a car bumper.

EMT and fittings would not have held up for typical damage due to raised elevation above grade and someone just stepping on it.

I also find the strapping of the box for support interesting.

Is there a disconnect on that box?.
Reason I ask that is because, I'd hate to be making a call and have some impatient guy, switch the phone off on me.

The 120v is for the booth lighting.
The telco provides a diffrent dial tone for payphones. Most never notice the difference.

Makes you wander if there is an earth wire in that conduit.
It wouldn't be great to rely on that rubber bonded link for an earth if the conduit was the earth conductor.

Awesome!