Partly it's that nothing else has ever really been as congenial (though G+ has engaging enough social elements that wrapping it around their blogging platform should do the trick) but partly it's this; Livejournal has never stopped being a frontier town.
Even now, in its dotage, it's still a place of ruckus and riot. Malware, bot and cyber-attack developers dance through Livejournal, their favourite sandbox, locked in scrappy conflict with archaeological layers of baroque improvements and their angry eldster developers. Vast, incomprehensible political crises sweep over-head leaving puzzling pronouncements and gaps in service. Random grudgers slip knives of angry code into ancient ribs. Spam-bombs drop daily and each morning is marked by sweeping the comment-splatter from broken captchas.
A few of my more popular posts are on a comment-spam testing list, so I always get to see what flavour of bollocks the spamsters are peddling; and the last one I saw before the DDOS curtain came down was selling Facebook friends, at $0.10 per 100. Viagra is tapped out. Cialis is gone. The future is social, as a million million marketing seminars around the world will tell you, and tell you, and tell you, as they staggeringly miss the point, yet again.
The social web is under attack from those who are fundamentally misunderstanding the advantages to be gained from enhanced sociability; and Livejournal is still, after all these years, right on the frontier. Big enough to be a challenge, but small enough to tackle. Shaky enough to be vulnerable, but with enough invested presence to fight rather than fold. Old enough that there's always a crack to slide through yet fat with passionate protectors and champions ready to do your error-testing for you. Pretty much perfect, in fact.
Livejournal, the Elvis of of blogging platforms, I salute you. May you die on a toilet doing what you love.