Shell had to do this because of shell reasons, like how you need spaces where you shouldn't. Perl post-dated C by over a decade, so there was no reason for goofy argument unpacking.
So @_ was a response to that issue, given Perl was about being dynamic and not typed and there were no IDEs or linters that would type-check and refactor code based on function signatures.
JS had the same issue forever and finally implemented a rest/spread operator in ES6. Python had variadic from the start but no rest operator until Python3. Perl had spread/rest for vargs in the late 80s already. For familiarity, Perl chose the @ operator that meant vargs in bourne shell in the 70s.