|I see nobody answered #2 on that link above to an old post.|
Here is my belated answer:
This would be better directed to MS.
I would suggest it is an option for those with very little HD space to play with, who dont want to invest in a larger HD (or can't afford to) and are prepared to risk the consequences if they ever run into a serious problem.
Mass compression has always been a risky business even on much earlier OS's.