We do it because we can, mg. And because we're used to it. That's the way human beings are. Anything they can do, they will do. Using wood would not have to be a problem, though, providing there were the right reforestation programs in place, and no clear-cutting of existing forests allowed.

You might also ask why we are still burning fossil fuels when there are far wiser ways to produce energy...

or why we are still fighting wars when there are far wiser ways to spend time, energy, and human creativity...

or why we are still eating vast amounts of meat when it's not necessary or even healthful to do so...

or why we still have widespread poverty in the world...?

A lot of questions to ponder.