Interestingly to see a lot of questions about industry certifications. In my view, certifications such as Google Adwords and Hubspot Inbound Marketing offer following values:
Differentiate among peers: While certification doesn't ensure that one has acquired the relevant skills, having a certificate validates that you would have at least acquired the theoretical knowledge and thus can differentiate one with others who don't have it.
Preparation process ensures that you've acquired the knowledge: As I shared above, the process of preparing for such certifications ensure that one has acquired the knowledge needed to pass in respective exams. It also helps build self confidence.
Having said that, if you are really serious about building a rewarding career in digital marketing industry, your focus should be on acquiring practical skills.
Btw, we just wrote a detailed article about Google AdWords Certification.