The shortest sentences possible in English are overgeneralizations. That is, simple S-V constructions along the lines of “They run” describe stereotyped behaviors rather than any situation that ever has to occur in the real world, certainly not in any chronological or physical proximity to the speaker. This is a problem, what with the modern distaste for “labeling” – our language makes the broadest, most sweeping stereotypes the easiest to articulate.
It’s a cliché among language teachers that the “simple present” in English is neither simple nor present. On a conceptual level, it’s only simple to creatures like us with the human-like capacity for indirect association who can say “that thing may not be doing it now, but doing it is nonetheless part of that thing’s profile”. It’s easy to imagine it growing out of a need to describe the properties of nearby objects quickly and efficiently, a la “Snake bite! Human die!” I’m pretty sure most other species’ ability to link actors and acts is more limited to things currently in their stream of consciousness.
It’s very tricky to convey the concept behind this grammar point to learners via flashcards or other media, since the image on a flash card for “he brushes his teeth” is invariably someone brushing his teeth right now, not just someone who does it habitually. Some publishers put something that looks like a slideshow together to convey the normality implied in the simple present, but the point of the simple present isn’t that he has done it many times – it’s that he does it enough, given what our expectations are of the normal frequency with which one does that, to paint him more or less permanently with that action. Picking your nose once can be enough of a pattern to earn “picks his nose” added to your profile in the minds of your schoolmates, but missing even one day of deodorant means you are no longer thought of as someone who “wears deodorant”. As always, the grammar-translation that our students are used to complicates things even further – Japanese verb tenses pull double duty in different ways than English, the “present progressive” also describing habitual actions and recently completed ones, and the “simple present” also describing future actions.
I have an issue with the simple present – I think educated people should generally refrain from using it in its simplest form. Not simply for style reasons – or really not for style reasons at all, since the simple present is clearly as streamlined as language gets – but because it can’t help but blur the limits of our knowledge, exaggerating subjects to include more than they ought to and treating the actions of those subjects as if they occurred spontaneously and endlessly. A sensible stance to take on human knowledge is that it’s never more than a finite numerator over an infinite denominator, and hedge-free simple present declarations have a way of making that sound like something other than effectively zero.
It’s been a habit of mine at least since college to hedge in ways that to me show how much I care about the accuracy of my statements but to others sound as if I have little confidence in what I say, like “people say some parts of LA are dangerous” rather than “LA is dangerous”. Robin Lakoff might have called my speech feminine in this respect, and it would be if my goal were to show deference to male superiors. I’m not doing that, just trying hard not to go “on record” as saying something about groups of people that may be true for most of them but not all or not even most. The simple present is such a convenient but inaccurate tool for talking about large groups that you’re practically begging to be misunderstood by using it. So when I read criticisms like Lakoff’s on women’s speech or complaints about writing sounding “academic”, I generally think, well, more people should write and talk in ways that show that they acknowledge the limits of their knowledge that rather than academics and deferential types learning to exaggerate and generalize more to make their utterances easier to understand.
There’s a political issue here as well (obviously) in that some on the political right are wont to complain that requiring greater accuracy from simple present declarations of the traits of so-and-so group is “mere” political correctness and obfuscates truth. Basically, the kinds of sentences that are the targets of such complaints are slippery enough in who is captured under their single-word subjects (“Muslims”) and what their relationship is to their verbs and objects (“commit terror”) to count as garden-variety incorrect. To put it another way, “politically incorrect” assertions are more often too sweeping to be called correct in any sense. If someone cares so little for precision in communication that they can’t be bothered to season their simple present sentences with quantifiers, modals and adverbials of frequency (“Small groups of Muslims may commit terror under particular circumstances”), they probably don’t care much for the accuracy of their statements in general and shouldn’t be listened to. The simple present is as seductively simple as it is inevitably inaccurate.