The question should really be "why do addicts seek fame?"
If you look into their past you soon find they start with something small and take it too excess. It perhaps starts with drink or smoking. But the one thing that emerges over the bloke you see on the street drinking meths, is a massive ego.
In order to even become famous you have to survive some pretty nasty people out there. Some of whom will think your crap, have no talent, a drug addict, in it for sex, in it for the money, mad, a fool, evil, in with the devil, bent, gay (when you're not).... well you get the drift....
However others will think the sun shines out of your rear end
The addict also thinks the sun shines out of you know where, for themselves, till they meet those above and starts thinking it doesn't. And so has to escape.
In the Celeb case it started before they became a Celeb and the Celeb life is the escape. The only trouble is the Celeb is often one of those nasty people who say nasty things about others. So in the end there's no escape and you have people around you who are ready and waiting for you to fall. And if you fall off completely someone will profit from you.
However it works out in the end. For you can go on to your next lives knowing at some point in the future you can come back and write a book about yourself, or make a movie about who you were, safe in the knowledge that your a completely different person and even you don't know who you where.