It also comes in very handy when you need a 8m cable, but only can buy them in lengths of 5m and 10m, or when you’re wiring an entire building, and figuring out which lengths to order up front is a major pain in the ass, certainly compared to ordering a few hundred meters of cable, a few hundred connectors and tools to put the two together. And that’s ignoring the price difference.

As a person who has installed hundreds of miles of cabling of every description inside of buildings of every description:

Every single time someone has provided pre-terminated cabling for one of my jobs to "save time" or to "make it easier", this provision has done neither.

Instead, it has consistently multiplied both the time required and the installation difficulty. It has done these things while also producing an inferior end result.

It is my anecdotal observation that it's NFG.

It’s also about managing length and slack.

except those assembled cables will always be the wrong length.