That's because they do have it. It's called Adloquium. Effectively 675 potency (25 shy of Cure 2 and Benefic 2) and costs 1000 MP - same as the aforementioned spells. Same with Succor, though the MP values and potency fluctuate slightly between the 3 spells.

Also I've never seen anyone requesting a Physick 2. Probably because Adlo already does that intended function.