Not everyone wants the hassle of dog eat dog. Not everyone wants to be in an Arena full of people they would much rather avoid. Unless you are sat near the top of the UA the extra rewards aren't that great either.

I think half the problem is this was all forced on an unwilling population who liked it how it was. I personally didn't ask for bigger Arena rewards and I'm not too keen on this either. We as a guild played the Arena and did our best to be competitive-now that was fun. We chose to help each other out and we battled.

As for HP it gave the smaller players a chance to 'win' at something and gain some much needed rewards, which in turn helped them grow.