"Hey, if we make Google uglier, maybe people will use Bing!" "Probably not, but let's mess with 'em anyway."
Unless it was google.. "Hey, if we make Google uglier, maybe people will use Chrome!" "Probably, they are used to IE not working" Not sure who had the slip-up, but evil works both ways :P
I'm going to choose to apply Hanlon's Razor in this situation.
-How often do people who have to do something to detect chrome/firefox version? Unless you are doing something with bleeding-edge experimental APIs probably, never.
-How often do people have to do something for a specific version of IE? All the time.
Chrome & Firefox have been mostly compatible for the past 20 major versions. IE has yet to make two consecutive versions compatible with each other.
Also worth noting: Firefox and Chrome support more versions of Windows than Microsoft's past 3 Browser releases have.
Again I don't this is necessarily a distinct case of anybody trying to be evil. This is just a symptom of a bigger problem.