Buffer size is the product of bandwidth and delay, so if communicating with something close, it can still go fast.
Had an illustration of this once when my then-employers IT dept set up the desktop IP phones to update from a TFTP server on the other continental land mass. Since TFTP only allows one outstanding packet, everyone outside head office had to wait a long time for their phone to update, while head office didn't see any issue.
If it's a memory-constrained embedded device you're sending a handful of bytes of telemetry every now and then, not aiming for gigabit speeds. In fact it couldn't get to megabit speeds even if it wanted to. For something like that this is perfect.
Had an illustration of this once when my then-employers IT dept set up the desktop IP phones to update from a TFTP server on the other continental land mass. Since TFTP only allows one outstanding packet, everyone outside head office had to wait a long time for their phone to update, while head office didn't see any issue.