It depends on why the data was collected.
Globally the NSA and its friends collect it all.
If your telephone number is of interest, email, net use or social media use is of interest then its sorted, indexed, voice print is kept.
In the old days it was keywords, now its hops to people of interest and your own political, social activity and that of your friends or friends friends.
Your camera sensor pattern noise/noise signature, cell tracking, car...
Just the fact a person feels the need to use 'encrypted communications' found at a city, state, federal or international level makes them interesting.
The 'encrypted communications' would be kept, noted and the password looked for in past communications hinted at in IM or email.
if that fails and your still of interest - some form of key logger for the next time you encrypt or decrypt or open your application at keeps track of different passwords :)
An easy pattern might drop out of years of easy to find past passwords use that could be tested.
it really depends on who a person is, their friends, their friends of friends. Collect it all and sort is now the cheapest way of getting it all.