but as gh points out below - cracking your encryption at home is hard - not when you have serious processing power though like the nsa - and THAT is assuming they don't already have the key. I mean really - if I am the NSA it would be more fun to steal stuff than to crack it.
People also forget - its not like some geek is looking at your individual packets and trying to recreate them - this is all done with enormous processing power and very sophisticated data mining tools.
And to your point:
I could go into more detail, but your argument amounts to, "because someone can pick a lock, I won't bother to lock my door"
Actually - the argument is - the door has a glass pane right next to the lock - so what good does the lock do - sure it makes you feel better and in the dead of night - the breaking glass will give you a few seconds drop on someone - but then I argue the lock is not what makes you safe - the warning is - so forget the lock and the glass and install a motion sensor camera(or better yet - a dog - any dog that barks). Don't put false hopes in security that really isn't. I do lock my doors at night - but only because my family is silly enough to think it will help - so they sleep better.