Neither. Wanded magic is actually fantastic at dealing with practical problems (see: Molly cooking and cleaning with magic. You could do that with D&D magic, but preparing those spells would often be a liability, as it comes at the cost of more combat-oriented spells.)
No, the trees are still there largely because it’s funnier that way. I think I mentioned in book 1 somewhere, also, that Professor Sprout chose to preserve the tree in Hogwarts because of what a magnificent specimen it was.