You have , for example websites that say "your data is protected by 256 bit encryption!". What does that even mean? Is just encrypted in transit? Is it only stored in an encrypted form on the other end? What is the key and who has to know it?
There is also a pretty big disadvantage to using good crypto, mainly if you lose/forget the key (or password used to derive it) you are completely fucked.
And almost all users, and most IT folks and developers are too lazy to follow processes. Plus management and shareholders don't want to invest the time and money for training or implementation.
It can feel a bit "advanced" for the average user to setup, but if that is the case and they NEED privacy then they could use something like http://www.hushmail.com/ which will encrypt the emails (but only with other users with encryption keys). It's web based to there's the whole use from anywhere thing... Of course, just use Thunderbird and get the whole things for free :)