Brethren, I've been in the ...

Brethren,

I've been in the water treatment domain for only a small number of years but my question is why do we opt for RO membranes for domestic applications? I could understand the logic should the ground water have contaminants such as hydrocarbons or dissolved salts but in most places, an RO System only generates rejects. I believe simple Filtration (Micro or Ultra) coupled with Activated Carbon &/or UV does the job fairly well. I think I may be missing a point and would really love some direction. My apologies if I've intruded & digressed from the question at hand.