You appear to be thinking of the CPA requirement which is for accountants, not actuaries. I'm an actuary, and the education requirements are thin https://www.soa.org/Education/Exam-Req/edu-vee.aspx.

You could theoretically get certified with only high school and work experience, although I don't think any employers would hire someone without a bachelor's. The degree can really be in anything though as long as you've passed an exam or two, as this shows an employer that you're serious and have learned at least something.

I believe the system works in our case because there is an ecosystem of employers, employees, recruiters, and government agencies that all buy into the exam process. It's sort of a throwback guild system that's not very similar to IT certifications such as CCNA.