Browser support (including Safari support) is the main reason why expensive desktop Macs eventually become paperweights, as has happened to my father in the last year. Safari, Firefox, Chrome, all stuck at ancient and insecure versions, with the web slowly breaking on these older browsers.

Despite how glossy and powerful the machine still is, if it doesn't have a working web browser it's only semi-valid. Watched my Dad go through this three times in the last 20 years, and no stranger to it myself. My own current Macbook Air is just a thin client for a Remote Windows instance, but I suppose eventually that the browser interface for that is going to become a problem too, when it 'ages out'.