Patrick,
Regretfully I was only thinking of one LA and one particular site when I was writing that post. Fredrick Law Olmstead at Biltmore House outside of Asheville, NC. Practically every view, from the drive up to the house, views of the house and from the house were orchestrated. As an example, if you have ever been there you can stand at the front of the house and look out towards a pergola. The pergola looks farther away than it actually is. The treeline one either side of the view is angled towards the pergola.
Standing at the pergola looking back towards the house, the treeline (as it angles out from the pergola) "frames" the house and makes the house look closer and larger (as if he needed to make it look larger).
Suppose Augusta decided to plant a hedge row of azaleas and flowering trees behind 15 green. That would close off the view of the water on 16 and give a player a flase sense of security that they didn't have as much to worry about being long.
The reason, at least to me, as to why it's done and why they are still there is that as far as green's committees are concerned you can plant as much and as many anywhere you want. But to takes and act of God or Congress to take one out. Should architects have stipulations in their contracts that a course owner or club can't do anything to the course without approval? I remember a thread some time ago when Tom Doak was asking about a waterfall at the 18th somewhere. So if he decided not to incorporate into the design, what's to stop the owner from doing it a year later? Doak suffers the slings and arrows of the raters, nobody knows the owner.