Retractable leashes are super common, and this is unfortunate. They fall in a category of leashes that allows a dog to have more freedom at a longer distance from the person in control. These types of leashes are typically used by trainers for safe and controlled training in more open environments, to help with training things like recall. Extra long leashes are not intended for general use, but somehow retractable leashes ended up in this space.
The problem with using an extended length leash for general use, such as for walks, is the long the leash, the less control you have, the less ability to protect your dog or those around, and the less ability to communicate using the leash. For general use, a leash has more function than just keeping your dog attached to you. It's also a communication tool. Most people don't know how to properly use an extra long leash, and most people assume they exist, at least in retractable form, to give the dog more freedom.
Let's touch on that more freedom thing. If you're not training your dog using the leash, your dog does not need more freedom. Using the more freedom argument is easily interpreted as "allowing my dog to go anywhere they want" and you should not be allowing this. This gives the dog access to places they should not be in to do things they should not be doing there. Like going potty in your neighbor's bushes. This is actually considered trespassing and you can be fined for it. In fact, the only place on private property your dog has implicit permission to go potty is easements.
Another danger is if the leash is fully extended in an area with other people traffic, that leash itself is a danger to others. Because you have little control over your dog, you can end up tripping someone causing injury from that, or cause some other injury related to excessive retraction. There are known cases of amputated fingers from these things. Uncontrolled extension by an excited dog can cause rope burns if the leash comes in contact with skin, whether yours or someone else. This seems like a far bigger liability than should be considered for the luxury of more freedom.
Now for the part about the dog and your lack of control. If your dog is at all aggressive, he should be on a short leash, period. A fully extended 26 foot leash is a recipe for severe harm as you will not be able to control that dog adequately before a lot of damage is done. Additionally, if you need to get to something, you may have to find a way to retract that leash to control your dog to prevent him from being a danger.
Along those same lines, of caring for the dog and lack of control, I've seen a dog in my building recently where the owner just lets the leash all the way out at it's full 26 feet as he walks him on the sidewalk less than 4 feet from the road. This road has a decent amount of traffic, and all residents of my building must us it to access parking. I worry that one day that dog will decide to jet into the street and his owner will not be able to get control well enough to prevent a tragic accident.
This is a training tool. If you are not a trainer, if you are not using it in a training scenario, you should be using a normal 6 foot leash.
I'm a strong advocate for putting limits on leash length encoded into law. However, I would not place the restriction on the leash itself, but rather establish a distance from the owner from which the dog is considered in control of the owner. 8 feet seems reasonable. I might be willing to accept 10 feet. 16 to 26 feet is absolutely unacceptable. It's dangerous for general use for the owner, for the dog, and for the public around them, so this is about safety. Retractable leashes should not be specifically banned so that actual trainers can continue to have them in their training arsenal. But people out in public need to have them taken away.