the purpose is to make someone uncomfortable, it's a ritual of patriarchal chauvinism.

Part of it is doing it in front of other dude friends to reassert your masculinity and define yourself as "one of the fun ones", part of it is to get joy from making someone uncomfortable in a life where you otherwise have no power (other than making women uncomfortable).

As others said, I think it's just the power rush and probably also the subsequent sexual excitement from making someone else sexually uncomfortable.

There's a way to check someone out or compliment someone on how they look, catcalling ain't it.

I am sure there are many reasons but one of them, for me, is it must be some sort of power trip. An ego boost perhaps. It is strange and uncomfortable and many who catcall know this but do it anyway.

I have a theory that catcalling is a somewhat socially acceptable way for people with anxiety problems to mask their doubt and get someone's attention, albeit it's often harassment rather than genuine connection

What does that mean, someone please explain? Calling someone cats what?