I do not watch anime films, I do not follow manga, I do not recognize characters like some otaku addicted to this genre people. I know only Asuka Langley, though I have no idea what “Evangelion” is about.
But as a fetishist, I suspect that for most these cosplayers, collectors, otaku “following the plot” is just an excuse to play with fetish stuff almost no manga can exist without.
Look at the girl (on the photo) cosplaying a character from “Gantz”, or look at the collectibles on eBay (especially figures) from “Gantz” and “Evangelion“.
Yes, definitely and excuse. Just like Halloween, carnivals, Goth festivals or discos with a theme.
Thanks to Navi Arimeka (G+) See 6 images below.