The suggestion should be accepted if the material improves the literature review process. If not it should be rejected on the grounds that the material is not relevant to the current work. This process is better when it is a double blind submission process, which eliminates the bias in the suggestion and arguments can be done only on the basis of merit of the work suggested.
Yes, as a reviewer may eventually refer to other publications about the topic of the paper being reviewed to give honest feedback, and this will improve the reviewer's knowledge about the topic. In addition, by reviewing papers you can avoid the mistakes which you may encounter in the paper being reviewed in your future work.
The suggestion should be accepted if the material improves the literature review process. If not it should be rejected on the grounds that the material is not relevant to the current work. This process is better when it is a double blind submission process, which eliminates the bias in the suggestion and arguments can be done only on the basis of merit of the work suggested.
I have been through this several times. Sometimes reviewers suggested their papers that were not even close to my work, other times their suggestions are relevant. However, I cited only relevant publications and refused others by giving them a reasonable but soft and respectful response.
Yes it matters a lot. An irrelevant paper, if cited, may misguide the reader and bring frustration when such paper is difficult to find and/or on subscription-based. Why one would spend energy searching, downloading and reading irrelevant papers? This also questions the credibility of the citing publication because sometimes the reviewers' suggested publications are not only irrelevant but are of low quality, poor venue, have little scientific value.
Peer reviewers play a central and critical part in the peerreview process, but too often come to the role without any guidance and may be unaware of their ethical obligations. The COPE Ethical Guidelines for Peer Reviewers set out the basic principles and standards to which all peer reviewers should adhere during the peerreview process. It is hoped they will provide helpful guidance to researchers, be a reference for journals and editors in guiding their reviewers, and act as an educational resource for institutions in training their students and researchers...
"Does it matter, if the authors cited the reviewers articles in the manuscript ?… "
If it is relevant then it does not matter. For example, let say that the reviewer is the one that proposed the subject or methodology that is being used in the paper, then it is relevant that the reviewer's paper be included and a mistake on the part of the writer.
More nuanced scenarios based on relevance can arise, but the relevance test must be made and that is why it is not a simple yes or no answer.
The great work and effort of the reviewers should be noticed, but without self-promotion. Ethical principles of the profession and academic integrity should be adhered to.
Ljubomir Jacić You have mentioned the ideal case of how the reviewers and other professionals involved in the field of research should perform their work in a ethical manner and show the ideal academic integrity. Thank you for the guidance.
Muhammad Usman Tariq fully agreed with your concerns. The journals, publications houses, the teams involved with the journals and also the university system all are working towards the goal of high rankings and impact factor. In this race, I think science is compromised sometimes.