The vast majority of software is written for businesses and runs either on an intranet or is available on the internet to the users of that business.
That doesn't mean a thing in terms of scalability. One user can max out a fast machine with OLAP cubes or other DSS. Or any sort of simulation or modeling. Think in terms of datasets, not in terms of users (all many users are is a large dataset with a requirement for a quick turnaround of each computation).