a couple of reasons. If you can sleep perfectly well on an angled bed... that's fine. But if you can't, there's a point where practicality takes over and you make the best of the situation. What's the point arriving tired after a flight in business class if you can arrive refreshed after sleeping soundly in economy?
Booking economy is potentially unlikely to give you three or four seats to lie on... but if business class is the only class offered and you ask the crew to reserve a triple seat in economy (if loads allow), you'll be accommodated if they can. It's a one minute transaction, done discreetly. No one is any the wiser (except maybe your seat mate in business who thinks you were a seat poacher!!
)
You can always head back to your seat for the meal service before landing if you wish. (I usually just stay put and have the economy offering without all the fuss of the front cabin.)
) However - the economy seat issue is easily solved... business class duvet on the bottom as a mattress to smooth out kinks, economy blanket on top to keep warm if necessary. And business class pillow for comfort.
