Why celebrity blog or tweet?

When you start writing, sometime you are very clear of what you want to write. Sometime absolutely no idea. A celebrity like Amitabh can choose to write on very wide topic on his blog which though majority focus on his own promotion of acts and self praise though never ready to accept that he is self-centric. If somehow I came to mention of Amitabh and blog, so let share some views on why celebrity blog or do micro blogging (e.g. Twitting) today. I individually like to read about celebrities, their blogs, their tweets and all gossip mongers blogs/sites. I sometimes feel that being a techie, I should read more about technology rather the celebrities dishing their crap self-centric ideology's projecting they & themselves. But from childhood I am quite fascinated to larger then life people especially on show buisness. Why? Very hard to delve into that portion of mind but you can say I was and am star struck. So, when I came close to internet, I spend large if not all time on reading about them. And what the best way to know about them is to read directly from horse mouth i.e. read their blog or tweets. But slowly and steadily I am now getting irritated with it. And when I find reason to know, I found that they are using the platform for commercial reason rather then real intention to connect to their users/followers/fans. They never reply to comments of their fans and only RT (read Re-tweet) the good thing somebody says about them. They do reply or respond to famous or celebrities like them but never to their fans. People like Aamir khan are way ahead. He started the whole blog thing, if not originated, from bollywood fraternity. Idea projected that he want to interact with his fans but somwhere behind the whole black curtain is whole idea of marketing. As does he really? Never. He only uses the platform very cleverly for promotions of film by building hype very slowly on projects he is working on. The moment he jump on his project read films, he stop blogging siting reason that he is focusing on films. Oh really! Then how he do all other stuff in life like spending holidays or attending functions in between film schedules. And when movie is towards end, he suddenly remember and misses his fans badly and become active on his blog again. And we the very poor fans like big fat rat always catch in trap. Self pity but no rescue.

So what you guys think? Why these celebrity blog or tweet?