I don't hoard miles. But I do find it hard to spend them, mostly because most of our travel has to be booked on the basis of "We need to fly on X flight on Y date; I wonder if there's award availability?" - which is not conducive to being able to spend them.

Earning FF miles for the sake of hoarding them must be similar to earning higher tier membership for the sake of having the status; both of these are things intended to be used, not to be regarded as achievements in themselves.