No offense, but you are being a very precise in defense but very broad in your (in general incorrect) claim.

The representation of an image sitting in memory will be a bitmap array, and for sure that will compress quite well. Video data as well but any decompressed frames are so transient I agree they won't benefit. ML-models don't compress well, but training data certainly does.

If you put aside mapping already compressed or non-compressable data into memory, all the rest of the things ram is used for can be compressed. Day to day you will have a lot of memory allocated that can be compressed. Most memory in use right now on most computers is compressible.