The days of monthly CDROMs for fresh downloads
Back when I ran a BBS, I used to have a decent file section for my visitors. They could download a certain amount per day to keep from tying up the single line for too long. I didn't really care about reciprocating with uploads that much, as long as they didn't go hog wild and do nothing but "leech". The best users would mix their downloads up with message board chatter and/or multi-user door game play. Both of those added new content and "life" for other users to enjoy. With a critical mass of people doing this, things pretty much ran themselves.
Files, on the other hand, were always a pain. Having files moving around from one BBS's download section to a user's hard drive and then to my upload section and then repeating led to an amazing daisy chain of craziness at times. There would be garbage files added to the archives (ZIP files, mostly) to advertise for other BBSes, for example. This would cause the rudimentary "signing" to fail since the archive no longer resembled the original from the author.
That plus the ever-present problem of people repacking archives to upload them introduced the possibility of corrupt binaries at best and actively hostile things (viruses) at their worst. Accepting uploads for things the users didn't create in the first place was just a real piece of work. Sure, while there were tools to scan these things automatically, it was a lot of work for everyone.
It was far easier to just buy a CD-ROM from an aggregator every month or two to get a whole bunch of fresh files which had been vetted. Many of these came straight to the CD producer from the authors, whether by having them upload directly to the producer's BBS, or sometimes the producer would go out and download them from the official "support line" system. Either way, it meant you would be able to find the latest version of foo.zip and it would probably be clean and clear of evil things.
I added a CD-ROM drive to my BBS machine back when that was still a relatively big deal. It was a monster drive made by Mitsumi which had a weird sliding mechanism where the entire thing would slide out (to clear the computer's case). It then had a lid which when lifted revealed the disc mechanism which looked a little like a Discman. It was slow, but it got the job done.
I would just put those discs online from time to time and let people download whatever they wanted. I also would rotate them periodically to let people have a crack at things which had been offline on prior weeks. My whole system had the entire index online at all times even if the discs weren't so that my users could get some sense of their options when making a request for a specific disc.
Even so, very few of those files probably ever saw the light of day. Considering that 28800 bps was above average speed back then and a CD held ~680 MB (same as today), that's not too surprising. It would take an exceptionally long time for anyone to get a significant fraction of any one disc over dialup.
The final piece of this puzzle for me was getting the drive out of the direct serving path. That is, when someone went to download a file and the Zmodem transfer fired up (dsz!) , I didn't want it opening K:\DIR001\FOO.ZIP straight off the disc. So, I built something quick and dirty which ran in my system's download script.
This little tool looked at your download request list and would check to see if any of them was coming from a CD. If so, it would first copy the entire file to a temp directory on my hard drive and then rewrite the request list. When dsz started to send you your files, you'd actually get C:\CDTEMP\FOO.ZIP or something like that instead. It was smart enough to not copy files which were already on the hard drive.
Stuff like this is how I tried to keep things fresh. Having the latest in software made things interesting for people who cared about that sort of thing. Keeping my doors current worked for the gamer crowd, and message boards with shared "echomail" conferences from around the world were for everyone else. Of course, within a couple of years, the whole thing slowly burned out, and now that system is gone. Everyone migrated to using dialup Internet connections, and then broadband.
Still, for a while there, monthly CDROM refreshers were normal. That's just one more business model which made sense for a while and then went away once again.