Apple makes money by selling hardware and software, whereas Google and Twitter make money selling ads, which incentivizes them not to encrypt our data so that it can more easily be used to target users. Or at least that's what this post seems to imply: http://paranoia.dubfire.net/2011/11/two-honest-google-employ....
"For example, conversations which take place over iMessage and FaceTime are protected by end-to-end encryption so no one but the sender and receiver can see or read them. Apple cannot decrypt that data. Similarly, we do not store data related to customers’ location, Map searches or Siri requests in any identifiable form."
I'm not convinced that this story is necessarily reliable, but it's better than the reverse: http://news.cnet.com/8301-13578_3-57577887-38/apples-imessag....
And in Apple's statement on privacy: https://www.apple.com/apples-commitment-to-customer-privacy/.
"For example, conversations which take place over iMessage and FaceTime are protected by end-to-end encryption so no one but the sender and receiver can see or read them. Apple cannot decrypt that data. Similarly, we do not store data related to customers’ location, Map searches or Siri requests in any identifiable form."
As John Gruber says, "That last sentence separates Apple from many other companies." (http://daringfireball.net/linked/2013/06/17/apple-privacy)