In the case of a wireless card in your laptop or a wireless link you can be running at speeds ranging from 300Mbit down to 1Mbit/sec, or less.
In the case of a home gateway, my comcast's business class service is running at about 3Mbit/sec on the uplink.
Huge dark (unmanaged) buffers in the device affect latency really badly - not just for TCP/ip, but for stuff that would ordinary jump to the head of the queue - udp, dns, voip, gaming, NTP... ... and in some cases are so big as to break TCP/ip almost entirely.
We've been sizing device buffers as if it was all on gigE backbone networks. Nor have we been using reasonable AQM. I urge you to try the experiments mentioned earlier.