help this is driving me crazy

1: Someone may post a tweet, with a hashtag and a link.

2: When someone else does a search for a hashtag in the search box, that persons tweet will show up.

3:I posted a a tweet with a link and a hashtag.

4: The tweet shows up in my timeline okay.

5: But if someone else does a search for that hashtag, the tweet I did with a link wont show up.

Why is that?

Is it to stop spam?

Why do tweets from some people with links and a hashtag show up, when you do a search for that hashtag and from some
other people it doesnt.