Everyone has an HIV status; you are either HIV-negative or HIV-positive. Not taking a test doesn't mean that you are HIV-negative; it simply means that you don't know your status.
Many gay men don't know they have HIV!
Knowing your HIV status enables you to make informed decisions about your future, your relationships and the sex you have. If you have HIV you will be able to access treatment and make you less likely to pass the virus on to your sexual partners.