That's because pirates care more about user experience and know more about digital packaging than the publishers do. People getting content from pirates can just switch to another source at any time if one pirate does a bad job. People getting content from official publishers are stuck with whatever they put out.

There was one game (I think one of the really old Unreal Tournament games) that had all the sound files as .wav files, which made the game huge. Many people were still on dialup at the time, so pirating it would have taken over a week to download it.

Well, one pirate group compressed all the .wav files into MP3s and wrote a quick batch script to decompress them all back into the .wav's. Turned a 700 megabyte download into a little under 100 megabytes.

Jeez that takes me back. CORE, CLS... Some games were compressed with UHARC or ACE which performed better than other compressors at the time. mp3unpack or WAVE injector would also run to decompress the mp3s or recombine them back in to large solid files. All that while having some banging chip tune and a snazzy animation play. CLASS!

At that time it might also have been illegal to distribute an mp3 decoder without paying royalties.