You don't need that as much on modern protocols. The point of 8b/10b or 64b/66b is that it guarantees enough edges to allow receivers to be self clocking from the incoming bits being more or less thrown directly into a PLL.
The previously mentioned issue is that to never buffer packets in a reclocking repeater on a link, you _need_ the incoming packet rate to never be higher than the rate at which you can send them back out, or else you'd fill up/buffer.
If your repeaters are actually switches, this manifests as whether you occasionally drop packets on a full link with uncongested switching fabric. Think two switches with a 10G port and 8 1G ports each used to compress 8 long cables into one (say, via vlan-tagging based on which of the 8 ports).
The previously mentioned issue is that to never buffer packets in a reclocking repeater on a link, you _need_ the incoming packet rate to never be higher than the rate at which you can send them back out, or else you'd fill up/buffer.
If your repeaters are actually switches, this manifests as whether you occasionally drop packets on a full link with uncongested switching fabric. Think two switches with a 10G port and 8 1G ports each used to compress 8 long cables into one (say, via vlan-tagging based on which of the 8 ports).