Installing The Sims 3: Encountering Late Night

So, I admit, I've installed these games many times before. But I don't remember encountering this in the instructions of Late Night. The Instructions want me to uninstall all of the previous games and reinstall them without cracks. That's all fine and dandy, I suppose, but it doesn't explain why I need to uninstall all of the previous expansions and reinstall them. And it comes with it's own cracks for the previous games, can I not just install Late Night as per usual of the previous games and apply such cracks to each game after and have it still work? Does it need the original files from previous games to install? Because as I've said, I've never encountered this issue and I just don't want to screw up the game in the end and have to redo it all, when I can just redo it at this point, or just knowing it will be fine to continue as usual would be good.

A Little guidance I guess is what I'm asking for.


EDIT: My mistake, I uninstalled all the games and will reinstall without cracks until the end.