That's the thing with evaporation: you don't want your water to leave stuff behind after it evaporates because that will foul your equipment and cause lower efficiency.

You could in principle design systems with enough fouling mitigations that you'd be fine, but its likely that the cost of those mitigations is roughly the same as just purifying the water up-front.

Short answer: several operators already do. The barrier isn’t technical, it’s proximity to a municipal wastewater source and willingness to invest in on-site treatment (pre-filtration, ultrafiltration, partial RO, ongoing biocide dosing). Recycled water typically costs 30-50% less than potable once the treatment infrastructure is in place.