HIV tests cause a lot of anxiety. A lot of this is due to the ignorance is bliss philosophy: some consider it better not to know. This situation is not exactly enhanced by insurance companies, who consider the existence of a HIV test on the customer's medical records evidence of a high-risk lifestyle, and so charge higher life insurance premiums. Last, but not least, is the fact that they involve big needles and two test tubes of blood: not good if you have a phobia of either.
Bringing the subject up with a doctor or partner is also a little embarassing: wanna scream 'I HAVE A RISKY SEX LIFE!!!!!' from the rooftops? Didn't think so. Don't stress. Doctor-patient confidentiality, for a start. And partners? Well. Suggesting that they should get a test can be insulting, while telling them you want one may freak them out. But hey: embarrassment versus early treatment of an often-fatal disease really shouldn't be a hard choice.
Call me a fascist, but I've always believed that, if you are entering a sexual relationship and you think you could be HIV-positive, there is no excuse not to get tested. Your own body and safety you can ignore. Someone else's you cannot, particularly given recent rulings that infecting someone with HIV can amount to assault or manslaughter.