Teinen-go wa Isekai de Taneuma Seikatsu - Ch. 9

[SifTheFair]

Those are very situational and might not be worth training a high ranking officer nor staking your whole strategy on a single person. In other cases you would have to cast those in the timespan it takes you to be instagibbed by a fire spell, and you still have to sustain for longer to strangle someone.

I mean we can argue over it, "standard" offensive magic like fire, lightning and probably rock spears, should be already expected and maybe even planned around.
Impeding your army, be it by making the ground a marsh or just by throwing water at the soldier would require more than just a "counterspell".

Even then, and let's say they don't want to bother to train magicians for that, high pressure water spell shouldn't be "new", because water spells could just be a mimic of other offensive spells.

In the end, it's the fault of the author to not give a credible reason for them not using water magic, it makes everyone reflect poorly : the mother, the sister, the army and the research group.