The Mac world embraced Stuffit because it was the best choice of the compression programs in the early 1990s. Compact Pro was also quite good but was a bit slower, especially when expanding the archives. Stuffit was also shareware back then, meaning that distribution was quite good. (Compact Pro was too; programs like Disk Doubler were the commercial alternatives).
Users of Stuffit who were sending their files to others were supposed to use the self-extracting archive option. That way if someone was stranded in an area that didn't have a BBS they could just open the application from the floppy diskette. Compact Pro had this option too.
Too many people forgot to check the "self-expanding archive" (remember the .sea applications?) when they were working with Stuffit.
Stuffit became a victim of any software that gets too successful--it got to be a hulking beast of a product with too many problems. By the end of the 1990s I could no longer bring myself to use the new versions unless it was absolutely necessary (as was the case before I got a CD-RW drive to back up my data--otherwise I'd have to put a 1.4MB file on a floppy compressed, as so often happened with scanned photographs).
There was also the change of hands. Aladdin became Allume, which in turn was bought up by Smith Micro (the company that probably e-mails everyone on this board with a product offer every other Tuesday). I don't like the way Smith Micro handles Stuffit and I personally think they should make older versions of Expander available to those who might have old data sitting around that can only be opened on older computers.
If all else fails, try tracking down an old version of the shareware program. It just might work. (Bonus points if you try to register it).