yeah, i agree with you, water changes do make lots of sense, both for addition of elements and dilution of others. I dose my tank with certain elements, and should probably do some water changes every now and then, but it can be greatly minimized and it doesnt necessarily mean you are going to run into problems.. thats all...
One more point. If you arnt using real saltwater from the ocean (my LFS sells filtered ocean water), then you may also not include certain elements and minerals that the Salt Manufacturers have either left out purposely or accidentally... I am sure they have taken every possible course of action to ensure our salt water has all the elements scientists "think" we need to produce equivalent water, but anything synthetic is just not the same as the real thing.
I agree that there is no way we can produce what nature has over the last several million years, and as a result, we cannot expect our specimens to live out their entire life. But we can, and should, try to make a self sustaining system that requires little else than addition of as little amount of external sources of minerals and food as possible. This has been the focus of the hobby over the last several years, and we should continue on this path. Saltwater is so much easier to take care of than it was 10 or 20 years ago.. no filter changes, advent of nitrate removal, etc, etc....all though natural processes as well.... and who knows, in 10 or 20 years we may just figure out how to add certain natural items into our tank which will continuously feed and nourish our tanks as well...... we can have the "add water" and wait tanks in our future... and cool running lights that are twice as powerfully as the strongest MH bulbs.
But one thing is for sure, if we dont try and test and experiment, we will not move forward from where we are at today...
There is one thing to try true and tried systems, and another thing to try and figure out a way to improve it... I am trying the latter, and hopefully, if mine works out well, and others work out well (Plum hasn’t made water changes(a much longer time than me), and his tank is just amazing), we may have a new way of keeping saltwater tanks.