It’s not impossible. Rookie wages really is chicken feed, it’d be both profoundly insulting and quite possibly financially unsustainable for someone like Bags to all of a sudden find himself earning $50k/yr plus match payments, or whatever rookie pay is these days. What happens if he gets injured and doesn’t earn match payments? He’s quite possibly got a mortgage etc, and on base rookie wage that’d be hard to sustain.
People really overestimate how much the lower-paid players earn. And someone like Bags (who was drafted late and so hasn’t been earning full AFL wages since age 18 like a lot of blokes, and also who wouldn’t have ever been among the higher-paid guys at the club) just isn’t going to go quietly onto a rookie wage just for the hell of it. He could earn more at a local club and work full time on top of that. Sometimes aging star type guys - who’ve been around for a long time and who’ve been paid very highly at points during their career - might take a pay cut in their final year/years to help keep a strong young list together, especially if they’re planning on transitioning to coaching once they retire. I doubt someone like Bags has the financial resources to do that easily.