Twitter is easy to operate, its true that more common people use facebook then twitter but the following may be the possible reason why celebrities love to Twitter then anyone else -
- Its 140 characters and by norms spell mistakes are acceptable so its more convenient for celebrities.
- Twitter is even more comfortable on mobile and again the reason is spell mistakes are acceptable.
- Twitter have concept of following (FB added that very late) which means you can have millions of followers and can reach them with your tweets.
- Another reason would be Twitter marketing which was more tuned towards celebrities where as FB marketing was towards common man. In every geography first adopters of twitter were Celebrities.