On pillow blocks, if the disc was missing the grease would be gone in no time and you risked getting a hot spot. We still sold cup grease well into the 60's just because many of the old farmers figured grease cups needed cup grease. However, todays grease is so much better than the grease was 50 years ago, if I were to find a can of cup grease somewhere in the corner of my warehouse, I think I would put it on eBay instead of using it.
