Why do I have to use View>Message>Best alternative to view graphic?

Often in the last 3 years, back to when I was using Leopard, Mail messages would appear in my mailbox which obviously contained graphics or pictures but which didn't show up in the email. (There would be paperclip icon in the right column.)

By going to View>Message>Best Alternative I can get the picture to show up.

Why do I need to do this? I recall in earlier versions of Mail this never happened.

Is there a way in Mail Preferences to change that? I can't find any setting that relates to that.

I am using 10.7 Lion, I have Mail set to Classic Layout. Thanx.