What is the big deal with people not liking safety harness for kids? (are you for or against?)

When my two kids were little  I had one that was so attached she never left my side and one that was a runner, meaning if he seen something he liked he went for it. Really who could blame him, at the toddler stage he really didn't understand safety and there was lots to explore. I remember going to crowed places and always having to hold his hand or put him in a stroller to keep him safe. I remember thinking how unfair this was to him but necessary cause he still did not understand safety. He was to young to really grasp it. Then on a local giving group a mom was giving away this backpack harness for free and I figured why not give it a try. It will give him a little more freedom to explore the world around him with both hands and without having to sit in a stroller.  The first time we tried we went to a local mall and he was so happy to be able to walk freely.(he is not one to hold hands) You could tell he felt like such a big boy, but with that the looks started. It really did not bother me but it did cross my mind what other people seen. Did they think my child had turned into a dog? Did he look like a dog? Should I worry he will turn into a dog?
Either way his free sprite and happy face was worth it all. My hope was to work with him on what is safe and not and do away with the leash but my son had a different plan. The next day I put it back on him and he decided not to move. Yep, just stood there looking at me. So I took it off and off he went. I put it back on and he stopped again...off, he went off...on, he stood there...it went on like this for days before I gave up the backpack and went back to hovering over him like a crazy mom making sure he was safe till he learned what was okay and not. So for me it worked once and then nothing but for toddlers who it does work for it is a amazing product! It does not take place of teaching toddlers safety but it keeps them safe while learning. I say give them freedom, keep teaching and of course keep them safe! I am for the toddler harness, but are you? I believe toddlers are meant to explore the world and learn not sit still and walk in a straight line. Feel free to comment and let me know! I would love to hear other thoughts on this.