Sadly it's still using a flawed[1] trust model where you trust repositories rather than publishers. And the UI-shim over GnuPG is 'basic' at best (to put it politely).

To add insult to injury deb/dpkg itself actually does contain a mechanism for package-level signing. But as far as I know no distro is using it.

To add even more insult to injury, all mobile platforms and both Windows and OSX have more reasonable package security models than Linux today.

[1] This is fine for guarding against compromised mirrors - and not much else.