Back then, it was the easiest way to transfer or store files. USB drives didn't exist yet. Burning to a CD was more mainstream at the tail end of the '90s. Zip drives didn't show up until mid '90s and they were still kind of rare not everyone had a zip drive. And network transfers were basically out of the question. Myself my first PC had a 33.6 modem! And I knew a bunch of people that had a 14.4 modem! There were no cloud options as that just did not exist yet.
But pretty much everything had a floppy drive. Are they were also quickly abandoned because didn't have a lot for storage. And most floppy discs were made with very cheap materials so they broke very easily.