I'd venture to say ease of use. I mean AT&T had everyone's emails but still Facebook makes it much easier to infer and understand and expand surveillance. Getting targeted information might be doable in hardware, but mass surveillance might be much easier if implemented a little higher up, by a dedicated dev team which issues bug fixes and feature extensions, which can turn over a request by you in a fraction of the time and whos capabilities are far more mutable. Hardware is more capable but it's a lot more work