Oh, I absolutely agree that they can be a substitute, and can be misused. But I see a lot of people stick their children in carriers for hours on end without letting them move at all, which I don't think is good, either.
Originally, I was actually not stating my opinion, I wanted to share what I had heard from an expert pediatrician.

I don't use the leashes, personally, but I thought it was interesting to hear another angle - one that I hadn't thought of!
I guess this was one of my original points. Alot of parents do stick their kids in strollers for hours on end. I believe this is because they are so young and this is the safest option. I dont disagree with this. What I disagreed with, and I spoke of earlier is taking your children to disney at such a young age. Now dont jump down my throat, but I realize that not everybody has the situation that I have. I only had 2 kids and I waited till the youngest was 5 before I went. Mostly I guess because I am always struggling for cash and wanted to wait until they were old enough to remember the trip. It worked out perfect for me. My son, who was the youngest (5) at the time of our first trip, does remember the trip and it left such an impression that he fell in love as we all are. I strongly feel that taking a child at 2 years old, is not so much for the child as it is for the parent.
That being said, I feel that if a parent takes their child at 15 months or 2 years that is great as long as they can afford it, then god bless. I guess if I had the cash I might have done the same, because I love Disney that much.
But if you do take your kids at that age then a leash seems to be the obvious choice, even if the child is NOT a runner. At the age of 2 you definitely need to protect your child. So i no longer feel that the leashes are so offensive to me. But I do feel that a parent that uses them for their convenience and without regards to other people including their own child is wrong.
So I know that some families need to please all of their children and may have to take a child at such a young age because other children in the family would be neglected to wait 3 or 4 years to wait until the youngest is of the right age. But to have a only child of 15 months or 2 kids with a 15 month and a 4 year old, is a bit of a waste of money for the childs sake.
That was my original point and that is where you see alot of parents using leashes when they wouldnt have to if they have waited until the child was a bit more mature.
That is all I have to say about that anymore, and I definetly have changed my mind about the leashes, only to disagree about taking 2 kids at the age of 15 months and 3 years and insisting on using a leash, when waiting another year and a half would eliminate the need for the leashes and give the children a much better remembrance of their first Disney visit. Again for some families it makes sense because of the ages of the other children.
But if you have a 15 month and a 3 year old, why dont you leave them with grandma and take a trip with your spouse that you can truly enjoy and wait a year or 2 to take the kids.
Just my opinion please dont think poorly of me for seeming selfish, I am only a little frugal because I cannot afford Disney Trips that often. But even though I break myself I have done Disney several several times since our initial Family trip in the year 2000
I think I have done well. Every time I feel we can afford a vacation I ask where do they want to go, and time and time again they say Disney dad. That makes me feel good. They love the magic that they feel when they are there. It takes them away from the every day struggles at home and makes them sing and enjoy the corney rides and attractions that we do not mind seeing over and over. Now my kids are 18 and 21 and we cant help but count down the days until we arrive.
That I am proud of. I have taken other vacations with my son and my wife with my daughter. They go to the mall of america and my son and I have done raod tripd down the old Rt 66 that we love doing. But as a family its always Disney and it always will be. That makes me feel good and I hope that for everybody. So if you take you kid at 15 months then that is great, just be careful NOT to force it so much on your kid as to have them rebel and hate those vacations.
God Bless!!