Ask HN: Why isn't data in motion universally measured in bits?

Data at rest (as in storage) is reliably measured in bytes.

But data in motion is measured in bits in most places (ISPs) and in bytes in others (some networking gear).

For data in motion, bytes feels like a divergence from the widely accepted standard.

Maybe there are good reasons. Why are bytes chosen where bits are commonly expected? (Looking at you TrueNAS.)