Patrick
this is such a surprising question to me; from the subject line, I would have never guessed it. And I must be missing a lot, because I don't have a clue how to answer it. I'll tell you the first thing that came to my mind: it was something JES said on the Pine Valley thread. I went to find it so I could quote it right:
"Would it be an improvement if Pine Valley chose to clear out most or all of its trees? I think it would be the most visually stunning inland golf course on the planet. Would it change one iota of my strategic approach to the golf course? NOPE!"
Is that somehow related/an asnwer to your question? I'm not sure. Part of the problem is that I don't think I ever thought of trees as primarily employed as lines of demarcations between neighbouring holes (that's probably because for me, and for many years, I was in them a lot, so they served a primarily penal function).
In regards to the average player, I wonder if the use of trees is not more important than ever, i.e. with undoubtedly straighter ball flights today (for me there's no comparison between the new drivers and the persimmon ones) the penalty for a poor swing has been lessened dramatically, and removing trees would lessen it even more, almost to non-existence. I'm not saying every course, or even a large percentage of courses, should be designed to have that kind of penal element; but if an existing course WAS designed that way, you will lose quite a lot by removing the trees and not gain anything at all in return; that course won't suddenly become more "strategic", as it never had the 'bones' built into it for that kind of play.
And for the better player, I think all this may be even truer still; the removal of trees would not change that player's stratgeic thinking at all, but there'd be almost no penalty whatsoever incurred for a wayward drive or a bad decision. In short, a game that has already been made easier for the good player because of the new technology would be made easier still; not, I don't think, what you had in mind.
Again, I may be missing a lot here Patrick and misunderstanding the question, but the answer I've worked my way towards is "No, it has not diminished the need for fairway-defining trees; it has increased that need...but only on courses so designed as to require the specific kind of penal element that such trees provide."
Peter