Not all that long ago, fleet software defined a relatively narrow range of products that primarily were designed to track maintenance schedules and the related costs of vehicle operation/ownership. Integration with other IT functions meant that the fleet software might interface with accounting functions by providing summarized expense categories and rolling asset information.
Far too many fleets, especially the older and smaller ones, still rely on basic fleet management software, or generic office-suite database and spreadsheet software. If you looked far enough, you might even find a few paper-based systems still in use.