One advantage that’s often overlooked when the sling is being discussed: It’s quiet! You can sneak up on your quarry and, if you miss your first shot and your quarry hasn’t seen you, you get another chance. With a gun, you fire once and everybody in the area runs away.
I have a couple of those laser-sight slingshots - the first time I saw that on the interweb I was like “OH WOW I GOTTA GET ONE OF THOSE!” and so I got two.
Yes, you can make your own bullets for your gun - it’s kinda time-consuming and still costs money.
There are usually rocks lying all over the place, however! A slingshot and some rocks are the essence of concealed carry!
I’ll stop now.
Iirc, and I have seen them in person, slings are not “quiet”. They make a whoosh whoosh whoosh sound that can be heard from 50 yards away as the slinger winds up.