My thought is , if the app is free then you are their product so , they will need to know more about you so they can sell your information to advertisers.
Even then, if they delete (after they analyze and before backing it up), it would still be nice.
According to Bruce, some apps don't do that
According to the article:-
The problem is that these new "ephemeral" conversations aren't really ephemeral the way a face-to-face unrecorded conversation would be. They're not ephemeral like a conversation during a walk in a deserted woods used to be before the invention of cell phones and GPS receivers.
At best, the data is recorded, used, saved and then deliberately deleted. At worst, the ephemeral nature is faked. While the apps make the posts, texts or messages unavailable to users quickly, they probably don't erase them off their systems immediately. They certainly don't erase them from their backup tapes, if they end up there.
Ephemeral conversation is easy to promise but hard to get right. In 2013, researchers discovered that Snapchat doesn't delete images as advertised; it merely changes their names so they're not easy to see.
If the government demanded copies of those conversations -- either through a secret NSA demand or a more normal legal process involving an employer or school -- the companies would have no choice but to hand them over.
Even worse, if the FBI or NSA demanded that American companies secretly store those conversations and not tell their users, breaking their promise of deletion, the companies would have no choice but to comply.
That last bit isn't just paranoia.
We know the U.S. government has done this to companies large and small. Lavabit was a small secure e-mail service, with an encryption system designed so that even the company had no access to users' e-mail. Last year, the NSA presented it with a secret court order demanding that it turn over its master key, thereby compromising the security of every user.
Of course, the typical Snapchat user doesn't care whether the U.S. government is monitoring his conversations. He's more concerned about his high school friends and his parents. But if these platforms are insecure, it's not just the NSA that one should worry about.
We need ephemeral apps, but we need credible assurances from the companies that they are actually secure and credible assurances from the government that they won't be subverted.
The link below has more information:-
