Statistics could be misleading. Most of my C flights have been before HON was introduced (I have not been on a long haul LH C cabin after 2006)- where I would assume that all SENs are equal (where I was getting op-ups 50% of time on UA transatlantic as a LH Gold). I was told that there is "an opportunity to upgrade" using e-vouchers on a SIN-FRA flight showing C0 D0 J0- when I refused and asked why not op-up me, I was told I have so many e-vouchers, so why don't I use two now. To cut the story short, I ended up in C and they probably swindled two e-vouchers out of some poor idiot.