The Roman baths, which they built all over the empire, were communal bathing facilities, Hot and cold pools to suit. Don’t know what else you think “baths” might mean. The Romans were great builders and engineers, writers and record keepers, and we do know pretty well what they were up to.
I suppose that I think they used the water and for a lot more than baths. The baths might be a formal and decorative ending, like the fountain where this started.
Maybe “bathing” was more than it is, today. Your clothes were cleaned and the lice were removed. Something like that. Those cisterns probably connected to a lot more than this.
Modern archeology seems to paint ancients as simpletons. I think this work was more justified than just “baths”. That’s all.