Yes unencrypted is easier, but it's not really much more difficult to use encrypted links. And usually people who aren't tech savvy will be following a guide provided by whoever is running the service. Particularly when it comes to configuring IMAP/POP3 e-mail, you have to look up the host address anyway (although quite often it's obvious) so all they have to say is "tick the SSL" option or whatever, one extra click. Even my mum can manage that .
I agree that if it's suitable to e-mail it's suitable to FTP. Photos and stuff I'd happily e-mail, but there's a lot of stuff I wouldn't e-mail, or at least I'd encrypt first and tell the recipient the passphrase over the phone. I think the danger with FTP is that you can end up leaving stuff accessible without thinking of the potential consequences.
take your average Windows or basic Linux machine - nothing but simple ftp, not sftp etc. As for mail clients - there are a huge number of clients and scripts that can't deal with SSL. Additionally, it does NOTHING for integrity/privacy, as smtp to smtp relays are unencrypted.
With the 'if it can be emailed' comment, I did state 'in the same format' - ie if you need to encrypt to email, you need to encrypt to ftp...
Yes e-mail is inherently insecure even with SSL, of that there is no doubt. However it does protect your password, which I still consider very important because many ISPs use a single password for multiple services... if your e-mail pass is snooped, so is your password for anything else. Often there's no way to separate them, again it comes down to them minimising cost.
The difference with e-mail and FTP for me is that I seldom send anything of any privacy value over e-mail. On the other hand I do often want to access my files (documents etc) when I'm away from home, and I don't know in advance which ones I may want or need. Therefore file level encryption doesn't help much as I'd need to know in advance which files I'll need (or routinely encrypt them all). With secure login and encrypted link I can simply log on and download whatever I need without worrying about it or planning it.
As mentioned before, I'm probably more paranoid than most when it comes to information security, but in my opinion and for my circumstances it's worth the (slight) extra effort/overhead.