Yesterday my children climbed a tree! Now there will be people all round the world who are sitting there saying "So what?". Let me explain why this is such a big thing.
If you are a child in the modern UK the chances are pretty high you have never climbed a tree. Trees big enough to be climbed are old trees- old trees are often removed from public places like schools and parks because they can have dangerous things like dead branches. If they are replaced, and sadly it is often an if, it is with small immature trees that are too small to climb. Even if they are perfectly healthy trees may even be removed simply because they are big enough to climb and therefore there is a risk that a child could be injured falling from the tree. Likewise many trees will have lower branches removed so that they cannot be reached from the ground specifically to prevent climbing.
So much for climbing trees in public places. How about just climbing trees at home. Here we get to the climbing trees are old trees argument again. Aside from those families who live in flats and therefore don't have a garden most UK housing bought or rented by families with young children is new or recent build. Cost being the prime reason - availability being another. Such houses often don't have a garden big enough for an old tree (it would take up the entire space) and haven't been established long enough for a mature tree to have grown anyway.
The image of childhood and playing outside includes things like climbing trees, making treehouses and rope swings from branches. Most of the children in the UK will be extremely lucky to be able to do these simple things that 50 years ago would have been much more common.
So if you do have a local climbing tree it is a privilege, don't just ignore it, let your children love it and climb it!