As an atheist, the primary benefit of studying religions is – ironically – that it helps you stay grounded in reality. God may be fake, but religions as bodies of cultural practices are very real, and using the former as an excuse to refuse to learn about the latter means you're at constant risk of making up a guy to get mad at.
The secondary benefit of studying religions is that Roman Catholic heresies are objectively hilarious.
The third benefit is that you have the knowledge of bigots absolutely making shit up when they say bigoted shit is what their religion is about, and get to call them out on it.
I'd say that the third benefit is actually that it helps you realize that the contents of any given religion's belief system are incidental at best to the function it serves as a social organization and a body of cultural practices, and as such arguing with religiously-inclined bigots on the basis of what their religion is or isn't *really* about is just implicitly ceding ground to them for no real benefit.
