Because It's Cool
This is a fairly weak reason in comparison to others, but I don't think it can be ignored. This may be one of the most overlooked factors in gun ownership. Someone goes shooting with a friend, loves it (and/or thinks the gun is just groovy), and soon becomes a gun owner himself (or herself). No problem there - everyone has to start someplace.
On the bad side of this equation would be those who want a gun simply because they think it will make them cool, or powerful. This is fallacy, and can be extremely dangerous.
Don't buy a gun to try to make yourself feel big... it won't work and when you get to showing off in an attempt to inflate your flaccid ego, things could turn deadly in a half a heartbeat. Forget about it! Buy a trendy car if you just want to look cool. Then buy a gun if you want to defend yourself against car thieves.
Family Legacy (Because my Parents Owned Guns)
A family legacy of gun ownership is often a factor in determining whether one will become a gun owner. Many of us got our first guns as gifts from parents.
Sometimes it doesn't seem to "click," and at some point in life the son or daughter decides that gun ownership is not for them. In these cases, it often seems that a parent's lack of care is what prevents these folks from feeling comfortable with guns. It only takes one negative experience to solidify a bad feeling towards guns in a young person.
When the parent has taken more care to teach and exemplify proper gun-handling skills and other firearms knowledge, there is a much greater chance that the recipient of this legacy will embrace (rather than reject) it.
If you have had a bad experience with a gun in the past, that may be a valid reason for you not to own a gun - but probably not. It's more likely that you have an irrational attitude towards guns, and unreasoned bias is never good.
Just For Hunting
Hunting is a fine reason to own a gun - or several guns. Different game calls for different firearms, so there's good reason to own a number of shootin' irons if you hunt various game. Owning guns only for the purpose of hunting is probably pretty common here in the USA... though many hunters, through exposure to and experience with firearms, become comfortable with them and often wish to own guns for other purposes as well.
If you want to do much successful hunting, guns are usually necessary. Some game can be hunted with bow & arrow, but the lion's share of game taken today falls to gun hunters - and thank goodness for that, because in many areas of the country even gun hunters don't take enough deer to meet management goals. And when someone is just beginning to hunt, it's best for that person to have every ethical edge, so it doesn't become boring or tedious.
Bowhunting is often the realm of the experienced gun hunter who wants to get more hunting time in the woods. Most folks shouldn't plan to start out hunting with a bow, but should instead use a quality gun and learn how to use it properly before heading to the woods. This increases one's chances of success, which helps keep one interested in hunting.
Target Shooting Only
Some folks just enjoy the challenge of punching paper with their guns. Shooting accurately is challenging, and many of us feel a sense of achievement from being able to put our shots exactly where we want them to go. The pleasure one derives from this is relative, just like any activity or hobby - but I don't know of anyone who likes to shoot inaccurately.
Competitive shooting helps some shooters focus and gives them a sense of belonging, as well as a sense of achievement when they are able to shoot better than their fellow competitors.
For Social Reasons
Some gun owners may own guns simply so they can take part in social shooting activities, such as sporting clays, cowboy action shooting, and the like. I seem to keep myself plenty busy with other activities, but for some folks this type of "social shooting" can become an enjoyable hobby in lieu of golf or something of that nature.
For Self Defense
This one is by far the most powerful, and universal, reason for anyone to own a gun. Human beings possess a strong self-preservation urge, as well they should - and a gun is very often the best tool one can have on hand to counter a threat to one's life, and/or the lives of one's family members.
Police cannot protect citizens, and even if they could, they do not have an obligation to do so. One must accept responsibility for one's own security.
To deny a human the right to defend him- or herself from any threat is the most grievous crime against humanity that I can think of. Human enslavement, you say? Genocide? Well, that kind of thing can't happen to an armed populace. Hitler's holocaust, together with a world war, began by disarming the German people. So to own a gun for the purpose of defense is one of the most universal and basic human rights - period.
Whether you're defending against an individual, a gang, or a government, gun ownership coupled with the knowledge and ability to properly use said guns is just about the most powerful force there is. An armed people cannot be enslaved, and as gun ownership increases, crime decreases. It's a win-win situation when more folks are armed. Many, if not most, instances of self defense don't even necessitate the firing of a gun - its mere presence is usually enough. (continued)