Also, they would have to actively target your phone for surveillance. I'm much more concerned about the passive interception aspect, and I don't for a second believe that I'm preventing myself from being surveilled.
The fact that they should have to go out of their way to break the 4th amendment is important to me.
Signal was intercepted:
http://heavy.com/tech/2017/03/wikileaks-vault-7-cia-bypasses...
My favorite most depressing take on this by Peter Gutmann - "Crypto won't save you either"
http://regmedia.co.uk/2014/05/16/0955_peter_gutmann.pdf