Indeed there are benefits. The benefit you gain in reviewing is getting to know what other researchers around the world is working on and how their works advances science and life. You also get to contribute your quota to helping to produce good papers that effectively enhance knowledge sharing and consequently, development.
Peer reviews are a service to self as well as to broader scientific community. Researchers performing peer reviews benefit as the process helps improve critical thinking, earn reputation as an expert in their field, and by building social capital with editorial team. Scientific community benefits by getting validation to research being published.
Reviewing the works of others is tantamount to lifting weights, as it strengthens our understanding and know how of the research work to see things from a different perspective, and to pass on the knowledge with our fellow future scholars
Peer review is the quality control in research community. It helps improving quality of any research. It also adds benefits to reviewer's horizon of knowledge and update. Some people ignore it, perhaps due to their time it consumes. But it is worth accepting to help build a better research community.
In summary, any paper that does not pass through peer review is like a job without quality control.
I think that reviewing for scientific journals is primarily the professional responsibility of an academician. (Of course, factors such as interest area, number and reviewing period should not disrupt the working order of the academician.) In addition; following scientific developments, contributing to the literature, breathing the academic athosphere and professional satisfaction are the plus gains.
Why review for a journal? There are great benefits to becoming a reviewer. What do you think?
Helping others to improve their manuscripts before publishing - ensuring a published article meeting certain standards.
Improving your own knowledge or learning through reviewing other research works e.g. mistakes you want to avoid or things you want to do / improve during your future research works.
While reviewing a manuscript, you are part of the process in contributing to knowledge - without you the manuscript can't become an article.
When you were approached to become a reviewer - It's a recognition for you as journal editors have reviewed your competency & experience and entrusted or empowered you to review.
You can earn some brownie points through registering your review works in Publons i.e. https://publons.com/about/home/
Any journal as a message for the readers & readers are selecting the journal for reading as its meets the requirement of their information & knowledge . In certain case as a matter of practice the journal are send to the author or writer for their opinion & review which may also get the information for the regular readers .
It is in this line some years back I have expressed my views in this matter which I submit herewith for your perusal.
To review either the publication of the article or even the a book of the author .The reviewer must have good knowledge with the effective presentation of the review totally in a impartial manner & he should not be biased for which he should appreciate the content of the topics which is not in the line with his thinking but he must give justice to his review .
To improve our work and keep with the latest in your field. Sometimes there is fine mistakes, they always do their best suggestions, so they are useful to our researches.