This obsession with airline upgrading never ceases to amaze me.
Would you go into your local car showroom, pay out for a basic Ford and expect (or ask for) a fully-specced Audi?
Would you expect your local supermarket to allow you to go and take 50% more off the the shelves for nothing when you reach check-out, just because you've chosen to shop with them?
I will agree that the airlines made it worse for themselves when they started upgrading many years ago to cope with overbookings, but pax still think it's the norm, and no, in most cases the hapless check-in person has no control over it whatsoever. The world today is run by bean counters, and as others have correctly pointed out the standard pecking order for upgrading is gold, silver loyalty card, price paid for ticket, etc.
Don't forget too, that there's an issue with meals. Airlines pay caterers ridiculous amounts of money for food, which is why so much of it is no longer available on shorter flights. Therefore, ordering say 7or8 more Business (or First Class) meals for each flight and then not using them is simply wasting a lot of money. Equally if people are upgraded, they expect an upgraded meal and accompaniments; therefore if there are no meals, there are no upgrades -simples.
If you're that keen to know what's it's like to turn left at the entry door, pay for it! Otherwise be content with what you've paid for.