It is a good catch word for theist to hate others, they are instructed to do so in their dogma and that is what their authority figure tell them to do.

"why does the word “Atheism” even exist? Is it useful?"

Christians find it useful, since many of them still believe knowing the name of a devil gives you power over him.
Plus I think a lot of them find Heretic just a bit so 17th century.

To not believe in God-figure may be an atheist universal. But the paradigm that each individual defers back to understand existence is anything but universal. That's why we are not a belief system.. We may be a lack of belief system by definition. But it ends there. Many of us may come to similar conclusions about the nature of existence,but in general we do not congregate together and declare it a belief system.

Before you call foul. The scientific process is exactly that, a process. It is a well established paradigm for collecting and sorting information. But those of us who whole heartedly prescribe to it, do not necessarily envision the exact same understanding of how the particulars fit together.

Read through the many comments about Atheism on this site and what you find is often, generally, self-congratulatory superiority, Atheists flattering themselves within this protected community. But, in truth, the only problem most Atheists have worked through is whether or not God exists. Beyond that, there's a lot of uncertainty and much of it relates to how to declare ones beliefs in the greater world, the world beyond this protected bubble, how to find acceptance in the world at large.
I am not an Atheist. I'm a nonbeliever. Many of my friends are religious, belonging to the greater religions and lesser religions and many nonbelievers. I don't see myself as separate from my religious friends. After all, we're all human. To my religious friends and non-religious, I am a nonbeliever and I am accepted, whether at work, in social circles, my neighborhood. I don't dismiss their beliefs or practices as inferior.
I think Atheism is still so misunderstood in 2018 because Atheists themselves don't know what to make of it. It's as if many Atheists are still in reaction mode, anti-everything they just rejected, still looking back critically, not quite ready to step away from that reactionary mode and into a new reality.

I like to remember a quote from a friend of mine (not sure if the words were his, but): "I'm not an Atheist. I just believe in one less god than you do." As human beings in general, and Americans in particular, we are raised that one must have "belief's" rather than just "ideas". We are taught that the answer "I don't know" is unacceptable. For me, the term "Atheist" just means "I don't know." And that's OK. Maybe there are some things we just don't get to know. Maybe we don't even need to know. What happens after I die? The only way to know for sure is to do it. I'm in no hurry to find out, and in the meantime I'd much rather focus on what happens BEFORE I die.

I totally agree on the word Athiest, I hate it. Religion wins when say we are without religion, we get sucked in. George Bernard Shaw Quote: "I learned long ago, never to wrestle with a pig. You get dirty, and besides, the pig likes it." They keep us busy talking about religion, when we should be talking about science and anything else that WE like. We shouldn't say we are without something. We need to stop using that name, because it contains religion. How bout philosopher, something with love of science etc. I personally like philosopher and free thinker.

To categorize the nonreligious. Plus its ingrained in their head when the word atheist comes into conversation their minds just shut down.

It's more to confuse believer's so they don't start thinking it's bad for business

So long as we are a minority, the word "atheism" is useful merely to label and distinguish us from the religious. So far as having to explain something countless times, you will never get away from this so long as there are propagandists out there driving their agenda. The kneeling of pro athletes for the anthem is another such case.

I prefer to say I am a Nontheist as people often confuse atheism with nihilism and think we have no beliefs or moral compass. I think religious leaders deliberately try to mislead their followers as to what an atheist really means.

As others have said Atheism is not misunderstood, it's feared. Religion is based on fear, admit it or not, and the fear of Atheism comes natural to the "believers" as we threaten their manufactured safety of the big sky guy and all the rest of it.

Atheism is not misunderstood, it is feared. There is no room in any religion for opposing views, let alone science. They want to characterize atheism as a "belief" so they can throw darts at it not realizing they are victims of Stockholm Syndrome in macro form.

Those who use religion to manipulate people need to keep their flock away from people who don’t need religion. They use the label “atheist “ to identify the people that their followers should be afraid of.

In order for the word "atheist" to exist, someone had to think of "theist". Kind of the chicken and the egg debate. In actuality, we existed long before any man made belief.

In this day and age, we are still surrounded by god fearing people, unfortunately, who are taught not to even think against god. To not live with god is too unimaginable for some.

Try to tell someone everything they know is wrong