Fair enough, have you asked the ARMv8 architect why he added them? He mentioned at ARM TechCon that there was a lot of thought that went into each change they made.
I would love to chat with the ARM guys and pick their brains. I suspect for a few things (like unfused branches) they wanted to match the existing micro-ops they were already generating since they would still have to support ARMv7!
But I'd also like to know why they didn't have things like AMOs (and instead had to add them in v8.1). And lastly, I would like to know why there is no Thumb for AArch64, and why it isn't the default ARMv8 behavior!
[1] Richard Grisenthwaite, Lead Architect and Fellow. ARM -- https://www.arm.com/files/downloads/ARMv8_Architecture.pdf