[lmgftp]

Simply because the vast majority of cases regarding visas/entry into the United States are determined by strict procedure and in accordance with the law. So most likely, as in the majority of cases, there is a reason we're not able to see here, for national security or one-sidedness.

[iskander]

I worked at a school with a high percentage of foreign students on F-1 visas. The visa-granting process is much more arbitrary than you imagine. The supposed "strict procedure" is actually filtered through many layers of several partially-communicating bureaucracies. An embassy in particular can approve or reject visa applications without recourse or oversight but Homeland Security can also erect inscrutable obstructions.

[genwin]

With no public oversight there's no guarantee the procedure is in accordance with the law.