Dave Ludlow wrote:
So why bother changing the name at all?

That sounds like "Why SI?". Note that there are many different units
of pressu
pascal
bar
atmosphere
inch of water
mm of water
inch of mercury
mm of mercury
foot of water
pound per square inch
pound per square foot
ton(UK) per square foot
ton(US) per square foot

Aviation has been using multiple units for weather (inch of mercury,
pascal, bar). More units are in legal and technical specificiations
(pound/inch², ton/inch²). Units of measurement for aviation are of
international importance and agreed via ICAO. It has compiled a
standard set of units:

"The standardized system is based on the International System of Units
(SI) and will eventually eliminate the use of different units of
measurement for the same quantity and provide for the standardized
application of all units of measurement for those quantities used in
air and ground operations."
www.icao.int/icao/en/pub/memo.htm