Presumably that utility depended on OS APIs and libraries, though? My guess is this app would probably have been similarly small or at least much smaller if it

Presumably that utility depended on OS APIs and libraries, though? My guess is this app would probably have been similarly small or at least much smaller if it had used a systemwide installed framework (i.e., Win32, systemwide .NET Framework, or System XAML/UWP) instead of bundling its own. But that approach is out of fashion because app and framework developers don't want to be tied to the OS, have to wait for their users to upgrade their OS before anyone can use new features, be tied to the OS support lifecycle, deal with compatibility issues and dependency conflicts, etc.