The most important reason to tweet is to give your followers, and others, access to your thoughts, ideas, experiences, as they might expect from the type of tweets that attracted them to you in the first place. In their eyes you have put yourself forward as someone who will enlighten them on a particular or related subject.
Justin Bieber tweets about Justin Bieber. His followers would not expect him to enlighten them on rocket science. If he did, the likelihood is that the majority of his followers would not take any notice.
It is the same for you. If you tweet about a particular subject, you are putting yourself forward as someone:
- who knows about the subject
- has an interest in the subject
- can point others in the direction of interesting information related to that subject
- has an opinion on the subject
- any combination or all of the above.
Note the third item: "can point others in the direction of interesting information related to that subject". Your audience has an interest in what you have to offer, why else would they be followers? If you follow others that have similar interests to yourself, it is inevitable that they will gain access to information; have personal knowledge of the subject; have their own opinions; that they can pass on to you.
They will post tweets that are of interest to you. Those posts are most likely ones that will be of interest to your followers. And the only way they will see the information that they are expecting you to feed them, is for you to pass it on: just like you would in the real world "Hey John, I just heard about a great.......".