Because people are better in nature.

Jena McGregor, writing in the Washington Post:

After more than six years of planning and construction, the massive urban garden is now open for employees to hold meetings beside a cascading waterfall, brainstorm in a third-story “bird’s nest” or crack open their laptops and work amid a lush array of ferns, tropical plants and a 50-foot ficus tree nicknamed “Rubi.” For now, Amazon employees will have to reserve a time slot to enter the building, but over time will be able to come and go from what executives call an “alternative workspace” that’s aimed at boosting collaboration and creativity.