Rear axle/brake drum gasket, why ?

Decided to pull the drum's to paint them and chamber the outer edge of brake lining for easy future removal. With 6800 miles I had to use the threaded holes to force off the drum with the gasket holding like it was glued and rusty... Nothing, like making a holding place for moisture ?

 

Maybe for metal on metal contact?

 

I routinely smear on antiseize between the wheels and the hubs to minimize the amount of corrosion "bonding" between the two. Maybe it's the same?
There have been times when a heavy rubber mallet was needed to separate them.

 

It’s so your drum doesn’t rust to your hub. That can be a real pain in the ass to separate.

 

Use of jacking screw is normal for brake removal on drums/disk. All the thermal expansion, weather induced conditions or simple over torque items will have said items almost seem it's welded together.

 

No gasket, it’s metals rusting to each other. Smear with anti seize.