why?

[Bounder!]

Have to agree with David (and the OP) on this. To say it doesn't matter that you can fly through trees because 'eh, you shouldn't be flying low' is silly imo - combat occurs at all altitudes. If that's your attitude then why bother having collidable buildings or even the ground for that matter?! Even if you start out at 15,000 feet, combat can degenerate to low altitudes as one party attempts to evade/escape. Being able to fly through the trees is a massive immersion killer and it makes tracking low flying bombers and fighters more difficult than it should be. Whilst there are more pressing issues with CoD, the non-collidable tree feature remains a pretty important issue imho and hopefully it will be fixed one day.