Someone said physics, it's also very common in engineering. But academically and professionally, I've only seen it with superscript.

Used that a bunch in physics class in school. Makes it much easier to calculate with units since you simply add up the exponents of the units instead of having to consider the notation around the units.

Doesn't work well in pure text mediums.

Pretty common physics convention, uncommon when referring to data speeds but common for other things measured over time.