Why does Disk Utility create EFI partitions on external disks?
So you can image the drive and get things set up while your new drive is in an enclosure and only swap it into your Mac as an internal drive once it is tested and ready to go. Also, not having to code special exceptions when to and when not to write an EFI partition is sound engineering practice.  

You can't write buggy code if you don't write any code.