I suppose there are two arguments, one is, "Let's make it easy for us to just have one kind of installer, that way we don't have to rewrite for different package managers!" This is essentially what flatpak and snap aimed to do. However, Red Hat were trying to force it on other distributions to accept flatpak as the 'de facto' package management of choice, just as they did with systemd (ugh!) and just as ugly Pulse Audio. Then Ubuntu pushed against this, developing an equally inferior product. I don't know what security issues there are about flatpak but I did post separately an article on why one should think twice before using flatpak or snap over apt: