That's my point, actually. People tend to assume that anything they do is being watched, where the truth is that whether or not a given item is stored depends on whether someone has specified it's interesting somehow, or whether a trained program has.
They don't store everything in case it's needed, nor do they have programs capable of detecting everything people suspect is monitored.
It's still an invasion of privacy and probably breaks various laws, but it's not the complete surveillance people tend to think of, and it's not as useful as you'd expect given the money invested and the effort put in to it.
> People tend to assume that anything they do is being watched
I'm pretty sure "every email, private message, text, search query, hostname/ip connected to, and call log of phone call you make" is pretty much "anything" for the vast majority of people.
https://en.wikipedia.org/wiki/XKeyscore#Workings
https://daserste.ndr.de/panorama/xkeyscorerules100.txt
https://www.wired.com/2014/07/nsa-targets-users-of-privacy-s...
https://www.theverge.com/2013/7/31/4574532/xkeyscore-data-tr...
https://www.theregister.co.uk/2013/07/31/prism_put_in_the_sh...
> The cover has been blown on an NSA program which collects data on “nearly everything a user does on the internet” even as the debate rages over the secretive US agency's mass surveillance of innocent people.
> The XKeyscore program covers emails, social media activity and browsing history
That's more than enough to store emails, unencrypted chats/messaging, gsm and voip phone records (metadata, and voice where available), GSM HLRs, and SMSs for all time; that's also the lower bound. Presently I'm sure it's expanded to parse and store as much metadata as possible that's ingested/processed by private data brokers as well, which as we now know are receiving copies of timestamped, precise GSM location data from many consumer apps.
https://techcrunch.com/2018/09/07/a-dozen-popular-iphone-app...
That original capacity estimate ranges up to 12EB and also was dated 2013; I would anticipate it to be at least 2-3x that by now, to be more like in the 10-40EB range.