Which raises the question: package management is just a bunch of nails; why do I need a specific hammer for each type of nail?
i call it "lazy opinionated adoption".
Why do you use apt in debian and yum on redhat?
Same reason as you write javascript for the browser. Just because someone put it there at some point. Would it be better to use python or anything else in the browser? sure! why don't you do it? because many people have done it before and there's no adoption!
package manager and languages are just like curl or wget. try one, command not found? try the other. meh. ...until you find people that assume other people can't learn. Then they will create a third option because other-people-are-dumb and it will be worse than both options you had before.