After we bought our house and I built my first raised beds in the backyard I thought I should explain what I was doing to my neighbor. I didn't want him to think I was just some crazy person who simply liked making wooden boxes. He stopped by once to ask me something so I explained that they were for my new raised bed vegetable garden. I was pleased with them and in my naivety I thought that everyone likes a garden.
The first words out of his mouth we're "they'll rot you know." Yes I knew that.
They're made of wood, they aren't weather proof. Organic materials will one day become part of the soil again. "They'll rot you know," not exactly a positive and uplifting statement.
That doesn't matter.
The box isn't meant to be permanent. Sure it's nice if it lasts for a while and you can get several seasons of use out of it. In fact mine did. They lasted about three years before needing replaced. They were untreated pine boards but even treated wood, cedar, and redwood succumb to the rigors of Mother Nature. Wooden raised beds will eventually become compost.
But it's not just about the box. It's about the experience.

The years of knowledge and experience I gained as a result of those first few wooden raised bed are worth much more than the replacement value of the lumber. The crops of vegetables that we've harvested easily cover the cost of the boxes - many times over. Most of all though the experience of growing, learning, and teaching my children about the garden has been priceless.
Building a raised bed out of lumber "will rot you know," but the experience gained and the benefits of that raised bed garden won't - because it's not just a box.