Because for less than the cost of an economy ticket, I can use an upgrade voucher (lloyds) and Avios I have collected through everyday spending to fly on a refurbished 747 in one of the best seats in the sky (according to flyer talk) 64k on the outbound and inbound journey. I will have enough food and drink to keep me happy for the 8 hour flights, I will have had access to good lounges and I will have flown from a nearby airport without having to make unnecessary stops/plane changes. For a thrice-yearly leisure traveller - what's not to like?