I don't use email for communication so that's not a problem. I have often wondered about the same from a texting and even voice perspective. My thinking is that it's not needed and may be something that attracts more attention than the protection it is supposed to be providing.

I suspect the bigger question might be are you trying to make sure your SO isn't able to read anything or is this more about LE concerns. In the first case you might get something from it if you have good cover stories for why you need encryption -- otherwise you're clearly hiding something and that's going to prompt demands to explain. In the latter case, it's probably easier to simply be very careful with your written statements.

I use email communications sparingly but I have a ton of stuff stored on my separate hobby account...  a free account with a popular ISP...  Things like bucket list, research...  I have been thinking that a more email would be a good thing, considering recent revelations about key word scanning by the servce.