When your packet leaves a router at some-pop-some-port-wherever, that fiber isn't usually the same piece of glass that plugs into the next hop. There's a whole chain of amplifiers and possibly multiplexers that handle it between here and there.
Some of those provide reliable transport service, giving you the illusion of a fiber that never breaks, despite backhoes doing what backhoes do. Some of those shift the wavelength of your signal, letting you use cheap optics without troubling in the nuances of DWDM that packs your signal alongside dozens of others onto the same long-haul fiber. Some of those just boost the signal, along with all those others on the same fiber.
But what all those machines have in common, is that none of them speak IP. None of them touch the payload. None of them are capable of decrementing a hop count. They're "part of the wire" as far as the packet is concerned.
In my experience, this leads to two types of network engineers, separated by their understanding of these underlying realities.