Why can it take more than a month to find a reviewer? In the mainstream publishing model, it can take more than a month from the time a manuscript is submitted to the time reviewers are assigned to review it. I feel this is a bit unfair as editors from these publishers generally require reviewers to submit their recommendation within a month from the time they agree to review. I believe the effort required to review a manuscript is much greater than the effort to find a reviewer.

My question is: Why can it take so long to find a reviewer?
There are several factors that can play into this:


Some journals have a strong editorial hurdle, i.e., a high desk-rejection rate, and the editor is expected to actually spend some time on the paper to judge its suitability for the journal. Thus editorial handling includes more than just finding a reviewer.
Some editorial systems only indicate that a paper is “under review” (or similar) when a reviewer actually agreed to review the paper, while others already do this as soon as the first requests have been sent to reviewers.
In some fields, it is common that reviewers blatantly exceed the allotted review time, so that the journal requiring their reviewers to submit their reviews within a month may still result in an average review time of two months or even higher.
Depending on the availability of potential reviewers for a given paper in the field, some journals follow a strategy of requiring reviewers to submit a review quickly, but take into account that many reviewers reject the request and they spend a considerable time finding reviewers.
Both, editorial handling and peer review do not take much work time in comparison to the allotted time (a day’s work or less in most disciplines). The main delay arises from the editor or reviewer having to find time for this given their other academic duties. Thus, if for example, the editor is on a conference for a week, they have to catch up with their regular work and the editorial work afterwards, which may amount to a significant increase of the editorial handling time.
Some editors are just slow.