Same as it ever was. Remember when lens flares were The Cool New Thing and ridiculously overblown in every game that came out? Or when it was reflections, or shadows, or bloom, or...
Now, yes, unlike video games, movies are in fact (usually) filmed with cameras. However, lens flares are still an artifact—they don't exist in human vision, and we know how to get rid of them. We just choose not to.
Also, speaking as someone who wears glasses and has a bit of astigmatism, flares/haloes around lights aren't necessarily stupid or unrealistic (although the classic TV camera lens flare, admittedly not so defensible).