While getting a doctorate degree is essential to enter professional academic/research job market, it is obscure whether holding a postdoc degree is required or even preferred. In a study , 85 percent of the Ph.D. holders stated that this degree is needed in their current job, whereas only 40 percent of the postdoc holders found it either preferred or required.
To start with, it is important to recall that postdoc is just a transition state and cannot be considered as an ultimate career goal. Second, it is hard to generalize the significance of having a postdoc for all the disciplines, e.g. in physics almost all the Ph.D. students end up getting one or even two postdocs, while in computer science graduate students barely end up doing postdoc. Therefore, I would rather merely discuss the pros and cons and let the audience to conclude.
First off, postdocs are absolutely underpaid! In  it is discussed that
”A scientific postdoc with a doctoral degree (to be redundant) with 5 years of experience makes ~$4,000 less than the typical librarian and ~$5,000 less than the typical postal carrier.”
Now, why a Ph.D. would rather to remain underpaid after receiving the doctoral degree? Many graduate students, especially who plan to become a tenure-track faculty, choose to go for a postdoctoral research position to become more competitive, i.e. by publishing more peer-reviewed papers, applying for transitional grants and gaining teaching experience. However, it is crucial to know that doing postdoc does not necessarily result in all the mentioned achievements. One should definitely apply to join a reputable university and work with an expert professor; otherwise, he/she may not have productive years and lose the chance to compete with the peers. Finally, it is always a good idea to talk to someone who works in your research field and ask whether doing postdoc is a wise choice or not.