[slackingoff2017]

Yup, it's because for the longest time TCP was as aggressive as possible to get the most bandwidth.

Over the last 10 years networks buffers have become gigantic and sending packets as fast as you can causes standing queues that can be a dozen seconds long. This is where the lag comes from when someone on your LAN is uploading/downloading.

The lag actually gets worse with higher connection speed because the devices tend to have even bigger buffers.

BBL and to some extent VEGAS are smarter going about things. They attempt to maintain constant latency instead of maximum bandwidth. For a few percent less connection speed all the buffers stay empty and delay stays minimal