Every question lacking in research becomes closed by being flagged by the users in any community of Stack Exchange network; I am encountering this since I joined Stack Exchange network. But there's exception to this that in past, though there were some flaggable posts (lacking in research) on the English Language & Usage (EL&U), the moderators did not closed those posts. See the following screenshot: In addition to this, following are also the posts lacking in research (but were not closed):
What was the reason they were not flagged? Were the users not able to flag any post? or there were not any moderators?