These offer negative benefits - they're still sandboxed, isolated from system files, heavily censored for anything Microsoft doesn't like politically, subject to a single point of failure, subject to Microsoft arbitrarily changing the terms, subject to instant takedown if there's an IP dispute, subject to Microsoft's inflexible charging infrastructure etc etc.
Until the Windows store code signing is dropped entirely, by default, universal apps will remain parked solidly in failure mode. Switching from Win32 is hard for developers even if it's unquestionably better in every way. Universal apps *aren't*.