Well, it's never been a compulsion to give the certification to get a job. Nevertheless, it might add value to your CV and let employers or hiring managers know you are a Salesforce Platform Developer with strong expertise and knowledge.
And when you have certification, it brings about a bootload of career opportunities. Some employers prefer candidates with certifications.
However, Certification is NOT the only key to unlocking job opportunities as a Salesforce Developer; many hiring managers search for the platform's experience, skills, and knack, which they all assess in the interview process.