Water propulsion offers: 


– high performance
– non-toxic (low safety risk)
– ease of transport / handle on ground
– ease of fueling / refueling
– low handling and manufacturing costs
Рcan put it on a ride share without any trouble 
– good fuel economy
– good thrust

Low Cost secondary thruster (or even your Primary!) to satisfy the pending FCC regulations on maneuverability:
https://www.fcc.gov/document/fcc-updates-orbital-debris-mitigation-rules-new-space-age-0

When we can, we can point to section 53, based on the comments “rule that spacecraft flying above 400 kilometers must have propulsion or other means of maneuvering”