Occam's razor says it's because the capability to gather far exceeds the NSA's ability to analyze. The data they collect is probably run through basic automated

Occam's razor says it's because the capability to gather far exceeds the NSA's ability to analyze. The data they collect is probably run through basic automated analysis (probably keywords, sentiment, and social network analysis, possibly some attempt to correlate to interesting real-world activity like purchase of large amounts of fertilizer, etc). But mostly the cache is used for retroactive surveillance to catch colluders after an event. The data would also be useful for local law enforcement (a kind of "super tap"), and certainly they have the eyes (if not the skill) to analyze the data, but that's a political hot potato. (And thank God - there are plenty of local police chiefs just itching to send the SWAT team in to a family home based on NSA "cyber"). Note that one of the more useful and interesting uses for this data would be political demographic analysis more comprehensive than anything available legitimately. It could also be used to target leakers, especially if you could use devices to put 3rd parties in the same room. E.g. my phone hears or sees you and your friend together, even if you don't have phones.