When does a Mac user need a CRM that runs on macOS?
A Mac user needs a CRM that supports macOS when customer work must run reliably on the computer they use every day. That does not require a native app: a supported browser often provides the main workspace. Problems arise when an essential connector, import utility or calling component requires a different operating system. If your routine already spans 3 separate applications, the CRM needs to connect those tools without introducing another computer just for administration.
File handling and account access are practical tests of that support. Uploading a 20 MB proposal from Finder, opening an exported spreadsheet and reconnecting your email account should all work through the intended Mac workflow. A desktop app icon alone proves little about those tasks. The useful question is whether the complete process works on your machine, including any extensions or companion software the advertised feature requires.