Context - this kind of application, IM in particular (not interested in Skype for calls right now), which is as necessary as email to many people for work.
Perhaps they should bundle Outlook as well (they used to bundle OE)? And Office (like they do on RT). Lots of people use that to work. Let's also bundle DVD codecs since lots of people use those, and BluRay, just in case they end up with a BluRay player.
Oh, and a better photo-editing suite, since Paint is pretty rubbish and lots of people take photos.
And OCR software - that's pretty useful too. And you'll probably want to bundle VLC for the off-chance that you see a video that you can't play, and probably Wireshark because it's more powerful than netstat.
Oh wait - now Windows costs you $100 instead of $40.
Instead, why not let people pay $40 for the bare minimum OS, and let them spend $60 tailoring their OS to their specific needs by letting them buy the software they actually want from the Windows store?