Comment by dredmorbius

Since A/C (or similarly, dehumidifiers) function by moving a large volume of air over a set of chilled coils, one consequence is that dust tends to accumulate on those coils, and be mixed in with the resultant condensate.

If you're looking at grey-water applications (e.g., watering plants, flushing toilets), this isn't a major concern. But if you were interested in drinking that water, you'd have to run it through additional filtration steps, and it would tend to clog those filters pretty quickly.

(I discovered this tasting the water from a household dehumidifier tank some time ago.)

The constant dampness also makes the same condensate tend to hold mould or fungus, which may not be especially conducive to health, whether of humans, pets, livestock, or even plants.

Climates in which A/C is most likely to produce a large amount of condensate (humid climates) tend also not to be especially water-constrained, so that the optimisation of salavaging A/C water is limited at best.

Not to say it's never useful, but there are more considerations than might be initially apparent.