Back in the day, journal articles were cited something like this:
Christopher Tuckett, “Thomas and the Synoptics”, NovT 30 (1988), 132-57
There was a simplicity about this kind of reference, and it made sense of the practice of finding an article. For all but the most current issues, we would go to the bound volumes of the journal in question, and all you'd need for that would be the volume number, the year and the page numbers. To add the issue number would be superfluous. But I've noticed now just how inconvenient it can be only to have that information in the light of ever increasing access to journals electronically. You can make a rough guess as to whereabouts the page numbers might be in a given issue, but more often than not, one makes the wrong choice. I must admit that I am now adjusting my own practice and, as far as possible, adding issue numbers to my citations, so that one like the above becomes:
Christopher Tuckett, “Thomas and the Synoptics”, NovT 30.2 (1988), 132-57
Of course things are simpler when you are reaching an article through a search and you are able to click through to the article in question, but it's now often helpful to have the issue information handy for occasions when one is in browse mode.