User blog comment:IamJakuhoRaikoben/Chapter 326: Natsu vs. Rogue, Review./@comment-5496918-20130406150247/@comment-7418318-20130406160007

If Zeref really wanted to be killed by a dragon, he could have attacked Ancalogia, rather than flying away on the airship.

And if he really just wanted to die, there would have been plenty of options to commit suicide.

But it seems he doesn't just want to die, but die in a particular way, or archive something more with his death than just the end of his own life.