Actual reviewing of an article requires clear and updated knowledge on the subject as well as about the stage of contemporary research on the topic of article. It is a tusk of experts.
But journals, even the journal take Article Processing Charge and/ or PDF downloading charge at a very high rate and get a huge amount of profit every year do not pay any money to the reviewers.
I know some journals who pay 1000-1500 USD to the review article writers, but do not pay a single pice to the reviewers.
Why free service is expected from the reviewers where the target is business?
Why reviewers are deprived from payment for their time and high quality services?