They come with apps like gnome software as standard, so you never interact with apt/rpm, flatpak or (barf) snap if you don’t want to. You might not even know which you’re installing.
They come with all sorts of configuration utilities like networkd (In my gentoo days I used wpa_supplicant directly and had no desktop integration with the wifi configuration. I was kinda stupid lol. Don’t use a distro to impress people kids), gui tools to manage your users and groups and something called “firewall configuration” which I don’t know the package for but is preinstalled on my fedora kinoite machine. (They are available in the arch repos, but unless you know what you’re looking for you wouldn’t think to install them.)
CUPS is preinstalled. If you don’t use an “unbloated to the point of madness” distro like arch or gentoo you’ve probably never heard of CUPS or interacted with it directly, but it’s the backbone of the linux (and macos) printing stack. In other words, printing should work out of the box wheras on arch that involves a trip to the arch wiki.
Integration packages are preinstalled. Things like the daemon that allows youtube videos in firefox tabs to be controlled by the play button on your keyboard if it has one.
Polkit is preinstalled, which allows applications to ask for sudo privileges and shows a popup box to the user asking their password. This is something you need to install manually on arch and gentoo, assuming you want that functionality and wouldn’t prefer to just only allow privilege escalation via sudo.
Most packages which ship with systemd services on debian (eg apache2, snapd, docker) enable that service by default. On arch this is usually not the case.
3rd party debian and fedora repos ship binaries so once you’ve added them to your config they function identically to core packages. Most AUR packages have to be compiled from source either manually or through a helper like yay. (Note: there aren’t any helpers in the base system so you have to do at least one AUR build by hand before you get that part of the tech tree)
Even bash auto-completion is an extra package on arch. No really, open a terminal on debian and then type ls -- then double press tab. It should suggest valid arguments. This isn’t a thing on arch unless you install the bash-completion package
ls --then double press tab. It should suggest valid arguments. This isn’t a thing on arch unless you install thebash-completionpackage