Some key apps on macOS do sandbox themselves, most obviously Microsoft Office. The main issue is that the tooling around sandboxing is poor. If there are viola

Some key apps on macOS do sandbox themselves, most obviously Microsoft Office. The main issue is that the tooling around sandboxing is poor. If there are violations the best you're going to get is an opaque message logged to an unbelievably verbose log torrent. Also, the low level sandboxing APIs you need to really batten things down for internal components aren't documented. Chrome uses them anyway, and they just have to rely on the fact that they're so big that Apple won't break them. But if you're smaller, it's a risk.