Because IRC, ICQ, MSN, Lunarstorm, Instagram, all those PhpBB and vBulletin boards we all used to use (and still do) was never even "remotely usable"....

The only way facebook differs to most of them is that it markets itself to being a general social network, not one specifically about programming, horses, biking, photography or another specialized field. Finding your friends by alias was never a problem, it's just like asking someone for their phone number.

Why? There are tons of online communities that mostly know each other by handles and still might profit from using facebook. Right now they stay entirely seperated unless everybody is OK with linking their "real" identity to their online one.

(If I wanted to contact you the ability to search for a real name would be completely useless to me. Being able to find someone called "baddox" might help. If that name then is linked to your real identity or not would be a different matter)