If the cage is rusty and mangled then the bearings and races are probably just as bad, usually forgetting to grease moving parts that require grease will do that... Pitted and rust infected are really 2 animals that shouldn't be compared.
I've used caged bearings and non, and I see many many more with a cage, probably because it keeps bearings from rubbing eachother, also because it's probably easier for the machines to put together quickly as opposed to needing humans that require toilets and food and money to do such things..