The burn rate numbers need more scrutiny as they include recurring expenses (salaries and materials) as well as one-time investments into Gigafactory and automated production lines for Model 3.
They burn it that fast because it brings more money in the future and they have funds reserve. Their net loss is getting smaller proportionally to the revenue constantly. They could stop capital investments any moment and be profitable, but that would mean much slower growth later.
Not sure that's the case as looking at this graph from The Verge, their revenues are growing but their losses are also getting larger proportionally to their revenues.
