The airlines I'm referring (major domestic legacies) seem to have no problem filling the front cabin at the last minute with elite members who get upgraded per the normal elite upgrade rules. In most cases, they'd rather not annoy their most frequent flyers (those elite members) by selling upgrades to "kettles" before upgrading (at least the higher level) elite members. But they don't think that making award seats up front (which get relatively few takers anyway) weeks or months or earlier upsets those same frequent fliers.

It's different with longhaul travel where the "simple" domestic upgrade rules don't apply (and you can only upgrade with miles, possibly plus copay, or systemwide upgrades). There there's usually no horde of elite statusholders ready to fill up the front cabin, and so paid upgrade offers are more likely.

And it's yet different at those foreign airlines who'd rather leave most of the front cabin empty than making it available to anyone (miles redeemers, upgraders, etc) who doesn't pay full price ! Should we ask a separate question of whether those mileage programs are effective?