In fairness, it's only on the two cheapest Y class tickets. If I was a loyal Skywards member and had paid a full fare for flexibility, I would be a little pissed if I ended up in a middle row because someone who'd paid half my fare got the last window or aisle seat. I actually think it makes sense personally.
You don't have to pay it, only if you want to be certain of a particular perch for 14 hours!
Harry