How can finding out that a hypothesis is not correct be useful for a scientist?

It tells you what not to do and gives you an idea on what to change in order to achieve you long coming goal of the expirment

It helps the scientist get more data so that way it can become more accurate.
once it has been tested enough and the scientist has more data then it would be become a theory
you need a hypothesis to help with the trial and error

Hope this helps :)