To try to answer your question objectively and fully...
You have pickups that will be relatively quiet so for some they may not wish to bother with any type of shielding. But that does not mean that someone else should not or may wish not to do so.
Per the guitar wiring kit that you mention containing heat shrink, copper tape, zip ties, white push-back wire, black push-back wire and shielded wire.
If you are going to shield the guitar than it needs to be consistent as Mayfly said. However what to do if all the wiring is not shielded such as push back wire. That is where copper tape is used attached to ground to "shield" the cavities and the unshielded wiring in them from interference.
Per the output wire to the jack - often that needs to run from a body cavity through a relatively small hole where the output jack will be located. You cannot easily use copper shielding tape there or conductive paint. So if you use shielded wire for that purpose you have a solution to not being to shield by some other means such as copper tape wire that is unshielded going through that hole. A similar use for shielded wire is on a Les Paul for example between the selector switch and the control cavity where three shielded wires are required.
If you use shielded wire for all of the job then the need for copper tape is very diminished. Though some may elect to use some in any case in the area of selector switches and pots as whatever wire you use at that point and the controls themselves are not fully shielded.
Whatever method you use for shielding you need a continuous ground so any copper tape you use needs to be conductive for example and grounded.
Hopefully now this gives a good overview of when and why you or others might choose to deploy any or a combination of methods towards shielding a guitar.