> Desktop environments don't need that much sandboxing because there isn't that much crap going on

You're safe if you install only paid-for software from big companies and open-source software that hasn't been bundled with installer malware. And never install Flash or Adobe Reader. And keep your browser, AV, and anti-malware up to date.

The plural of unsandboxed desktop is "botnet".

Yes, this is tragic and a real threat to open software development.