Originally Posted by
Ryanardo_daVinci
The e-mail offers are not random. They come when Business loads are exceptionally light, or (more often) when Economy reaches capacity and there are still seats in Business, they try and squeeze out a bit more revenue before making op-ups.
That would certainly sound logical and was what I thought a while back, but I've now heard of them on lightly loaded flights too. When you think about it, that can make sense too as if you're not asked you might sit happily in Economy but if it's offered, some will succumb and pay for the upgrade.