So.... the answer to the question in the title is "by law". The article seems to answer a different question: "Why do Internet firms invest resources in implem

So.... the answer to the question in the title is "by law". The article seems to answer a different question: "Why do Internet firms invest resources in implementing software which aids the NSA's surveillance?" Because otherwise, the NSA will build it themselves, and force the companies to install it inside their datacenters.