One of the reasons trees in the middle of a fairway can be hard to accept is due to a mismatch in golf design principles. In other words, when it doesn't work, it isn't the tree's fault in isolation.
An old principle that myself and I believe a few others on here hold dearly is that of a golf hole being designed so that there is a teeing ground and a putting green, and obstacles are often in the player's way between them, so that a golfer must negotiate the best manner in which to take fewer strokes to get the ball in the hole.
A more common modern principle is that the route between the teeing ground and a putting green is a corridor of safety, and that obstacles and hazards are strategically positioned lining this corridor to penalise the wayward.
Both of these principles have resulted in some of the finest golf holes, but holes cannot easily work well when they try and marry both. Some of the examples of trees in fairways here are on holes that are truly designed as corridor holes, and so it is the inneffective use of the central obstacles and required different pathways that is as much to blame as the tree.