I see this when i check in for KLM but only on European routes. I usually travel business on med / long haul so do not see this, but their cabins are usually full in Business long haul.
In Europe you get an offer for around E 50 for an upgrade. Not a huge benefit as a Gold member with all the perks anyhow, but when only 2 rows are offered on a 739 these days, they can but try.
Great idea on long haul, and i am surprised by some of the Airlines mentioned. I know Malaysia Airlines have a set fee for an upgrade from Sydney…if there is space, you ask, and you are well dressed!