Maybe I'm missing something here but I see regualr comments about how people wouldn't use their miles for an international coach ticket, prefering to use them only for higher class seats, and I don't understand why?

Clearly those seats would be more comfortable but isn't there a higher rate of return with the lower cost seats?

For the (miles) cost of a 1st class seat, I can get 2 seats in economy. Sure, you get a bigger seat and for the duration of the flight, you may be a bit more comfortable but is it really worth it? I hate flying as much if not more than anyone else but I really don't see the value of burning a ticket for a -tiny- amount of added comfort. 9 hrs in a tube is sucks no matter how you slice it

Is this all there is to it or am I missing a bigger picture here?