Watering - at home as in commercial irrigation - tends to be needed during hot weather. Hot, dry weather conditions are not really conducive to mold or funguses - that tends to form in cool, damp areas.

"Full daylight irrigation" is the norm throughout the west- don't know how it's done in the east- but it is in the west that one finds the mega-fields.

The money? Absolutely. However, added expense for innovations has always been cited as a deterrent to existing technology, and yet it somehow it always has been incorporated with not a whole lot of fuss. Think: electric wiring into homes, burying utility lines underground, fuel injection instead of carburation (gadzooks! How IS that word spelt?) , automatic shifting instead of manual - I'm sure we can all think of long lists of upgrades and tweaks that are now part of the norm but all were expensive to instate.

"dogs or kids drinking out of the toilet"? First, I long ago learnt to put the cover down and if people were worried about it, they could all learn the habit. (What else are the cute lid covers for if it is not display?)

For that matter, I suspect that far more kids drink water in their baths than drink out of the toilet!