TbyZ - There have been quite a number of sensible reasons offered for using water changes as part of your maintenance regimen. Just to recap:
1. Regular water changes can greatly simplify your set-up. 100% or 200% monthly water changes would completely remove the need for basically any other equipment. No dosing equipment, no skimmers, no carbon dosing, no algae refugium, no MarinePure blocks, no Triton testing - really, with enough water changes what else would you need? For a small tank or for a person with limited space or a limited inclination to deal with equipment - this is a great option.
2. While you can certainly reduce nitrates and phosphates without water changes, some people don't wish to grow algae or bacteria. I read a great quote on this forum a while back that made me laugh. Something like - "I didn't set up my aquarium to grow bugs and algae. I set it up to grow coral."
3. For some of us, water changes are *part* of our dosing schedule. It is easier to do a small calculated water change than dose 6 or 7 additional elements.
4. Dosing is not exact. I know with pretty good certainly what is in the salt I use. Do you know with certainty what you are putting in your aquarium when you add that AquaForest grab bag of trace elements?
5. People often deal with elements in excess of NSW. And sometimes they are content to simply manage those excess levels with water changes. For example, many foods contain high levels of zinc. But I might be very happy with the foods I currently use and would prefer to manage zinc levels with water changes rather than "eliminate the source" of the excess zinc.
6. Depending on the set-up, water changes can be cheaper than investing in dosing equipment, a refugium, a skimmer and such.
And so on. This is a complex hobby. At this point in the discussion I am not sure what you are trying to accomplish?
Firstly, I'd like to say I love algae & bacteria & everyone should.
There's another argument
I’m not arguing for people to stop doing water changes, or that there aren’t reasonable reasons to do them. I’m arguing the case to establish what legitimate reasons there are to do them, if these reasons are valid or just assumed, & what other measures could be taken to negate them.
A possible build-up of toxic dissolved organics may be a case against long term no water changes. But this isn’t necessarily the case.
Another, Randy pointed out, was high levels of inorganic trace elements introduced to the aquarium via sources such as food, pumps, etc. But again, this isn’t the case for all hobbyists, it can be measured & dealt with a least to a degree, and regular water changes of typical volume not only do little to address the problem, the salt itself can be the problem.
I still do water changes. I live 5 minutes away from an easy collectable source of pristine NSW. But not everyone does, & not everyone has a great source of town water to pour through their RODI units all day long. Some people have only bore water for instance, & that can have unimaginably high TDS levels. Hello filter replacement salesman.
And there are very successful tanks that apply the no regular water change method, like glenf DSR reefing.
There’s lots of arguments go on in this hobby regarding the best way to do things, what equipment is good or not. Gets heated, very political. Some people get very upset at anyone who argues against their opinion.
I’ll have people here hate me for this thread alone, for sticking to my guns if nothing else. So be it.
By arguing, or debating, you see others opinions, & I learn a lot.
There’s plenty of people happy & willing to argue with me.
But if nobody ever argued the point things would never progress.
I've gotten all I hoped to achieved out of this thread, and thank everyone who took part.
We do send in ICP-tests and adjust most of the measurable parameters to where we want them. In some of our systems we do small water changes. This is becuase we need to backwash our sand pressure filters(2-5% per month). But we also have tanks with great SPS-growth were we havn't changed any water in 4 years. 
