@yohanip 1 nonce = 4096 scoops, 1 scoop = 64 byte
4096 x 64 byte = 262.144 byte = 256 kbyte
A nonce is a chain of hashed scoops (4096), starting with the nonce and account-id.
You can see it on the right side of this diagram (Plotter).
It would be possible to compress it, but it would make it really hard for the miners to read the scoops, because every round just a specific scoop needs to be read. Also, because of the nature of compression algorithms (they remove redundancy, and in a plot file there should not be lot of redundancy), the compression of binary data often leads to bigger files.