Some people think they dont seem to do anything. I'm not one of those people.
I mainly let the solvents do the work and then use the snake to clean it out. I also tend to clean frequently, so I do not let a lot of carbon or copper build at one time. For this, the snake works great for me. I can more or less get the bore spotless with this method.
I doubt it'll work so well after firing 1000 rounds of corrosive, dirty AK ammo, though, but I guess it all depends on how well your solvents work. I just wouldn't expect it to do well under heavy grime.
IMO, the bore snake has two main uses. Easy, quick, bore cleaning, in the field, especially if it's something light, like dust or rain that got into the bore. And cleanings on guns without heavy fouling, where you can let the solvents do most of the work. I wouldn't expect it to replace a real cleaning kit, even though I exclusively use a bore snake on my Ruger M77 because it works well enough, for how I use the rifle.
The bristles also last surprisingly long. I don't know how many passes I have with my bore snake, easily a few hundred, though, and I've yet to break one, or mess up the bristles. Been using it about 2 years now, I've washed it a few times, and it's still holding up fine. Some of the weaving is starting to fray at the end because I let the bristles get caught on the end of the snake when it was getting washed, they got in there pretty good and I wasn't careful enough when I was fixing it. Not really a big deal as it doesn't affect the strength or effectiveness of the snake.