It’s significantly slower to access a disk than it is to access memory. When given a choice between using a bit more processor power to decompress the information once it’s been read into memory or pulling more information from the drive then you really should make the smart choice.
Even if disk space is cheap/free, it doesn’t make sense to spend the time reading the information whan you could be using it. The problem is of course, using a sensible and fast compression/decompression algorighm, and also realizing that it really screws with the whole ease of write on the disk. You end up with some change one byte means completely altering the on-disk image so you need to write a lot more information. This is probably why we use transparent compression on files that don’t change that much.
Whee, ain’t science fun.
If it wasn't for carbon-14, I wouldn't date at all