I'd also like to add that we forget that we're doing it, or at least I do. Once you set something up like that, there's never any reason to get rid of it; nobody is positively discriminating towards Linux.
I love when a ruleset (firewall, for example) has a "comments" field because I inevitably forget why I added something and then Chesterton's fence means I leave it forever, lest I spend hours a year later wondering why something broke.