Just curious, why do you care if you have one? Seems like overkill for pretty much any civilian situation.
Let me explain it this way as you are not a gun user. Why do you drive an automatic and not a stick? Worse, imagine if your car had three gears, but you had to stop the car to change from one gear to the next. Imagine if your cellphone could only do telephone OR internet OR games. Not all at the same time. Imagine when you bought a TV or DVR, it could only watch one channel or record one station and not several.
Would you consider any of the better, popular choices overkill? Of course not. The question seems ridiculous because you take your options for granted. It is the same way with a semi-auto. They have had semi-auto since the Old West because it simply makes the firearm better, more fun, easier to use for more stuff. Less hassle to operate. Better sport. Only from a military aspect does it also make the gun more potentially deadlier.
People would live healthier if all they ate was Kale. People would be killed in far fewer car accidents if they were all made to only go 25 mph. People would spend far less time on cellphones if they were only made to make telephone calls. People would spend more time with their families instead of watching TV if TV was only on from 8 to 11, and there was only 3-5 TV channels like when I was a kid. And guns would be less easily misused to hurt others if they only shot one round of .22LR at a time.
But just as no one wants to live on Kale, people want and need to go faster, cellphones are desired for other things, and folks will watch all the TV they can get, guns are both desired for and needed for more than plinking tin cans. The shooting and hunting sports is a wide and diverse field, firearms is a vast and proud tradition of history with many fans and adherents, and no one can define the needs of "civilian use;" just because today, they may sit in a closet collecting dust, or out on the field target practicing and competition or bringing home food, who can say what lays ahead a year from now, five years from now or 25 years from now? History shows that war, civilian suppression, oppression, and abuse are cyclic, and if it ever comes down to tyranny (and many feel we are getting close to that now), do you really want to be left there with nothing but your finger to point in your defense? Or are you just willing to lay down, surrender and die?
The one thing history teaches is that governments always act in THEIR best interests, not in those of its people. Only a fool thinks all these efforts to limit, restrict and ban guns is "for the public good," and once gone, you're not getting them back, and free of that restraint of an armed populace, even the best of governments with good intentions are now free to do whatever the hell they damn well please. I choose not to gamble on their good will.