Final answer:
The incorrect reason for the increase in STIs among gay men is 'increase in IV drug use among gay men,' as it is not supported by evidence provided in the texts.
Step-by-step explanation:
The question asks for the reasons suggested for the increase in STIs among gay men over the past few years, except for one incorrect reason. The correct reasons for the increase in STIs are 1) decreased fear of acquiring HIV due to advancements in treatment and a lack of awareness, 2) an increase in high-risk sexual behaviors among some individuals, and 3) increased Internet access to sexual partners which facilitates connections and potential exposure to STIs. The option that does not belong and is incorrect is 4) the increase in IV drug use among gay men, as there is no direct evidence suggesting that intravenous drug use has increased among this group, nor is it listed in the texts as a reason for the higher STI rates.