As far as selling the biggest difference between now and then was back then software could only be shipped on floppy disks, so it was more like manufacturing, warehousing, and shipping physical merchandise.
Right. Although it wouldn't have been practical for software that filled multiple floppies, by around the late eighties it was pretty normal to have drivers and the like available through BBSs. I don't recall most companies operating their own systems but this type of software was widely available through private BBSs--whether totally legally or otherwise. (It did seem to take a while for many companies to realize that they probably shouldn't make it hard for their customers to obtain the software needed to use the product they sold.)
Shareware was also widely available on BBSs by around that time although it was also distributed on floppies at Computer shows and the like. When I had a small shareware company starting in the mid-eighties the process of taking orders was still very manual--most orders came by mail with a check and I sent back a floppy (which I reproduced myself) in a mailer with or without hardcopy docs depending upon if those had been ordered or not.