Actually I have had more than one orthodontist telling me that it is better to get them when you are older. Often times kids get them at a young age and when they are taken off the teeth goes somewhat skew again due to their teeth not yet developed. It is better to get it when you are older as your mouth has then fully developed and any changes to it would be more permanent.
It gives your teeth time to grow out correctly. If you get braces as an adult they will be less effective because your teeth will already have grown out. If you get braces during childhood, it is easier to redirect the abnormal growth of the teeth than it will be when they have stopped growing.
Because your bones still aren't completely solid so when you get them straightened young they are more opt to stay that way rather then shift back into their original crooked position. Also with jaw problems it's far more easy to correct when you are younger.
It saves money and fixes the problem faster. I needed braces since I was 8 years old. I ignored that and I had to get bunch of fillings which is horrible. I take care of my teeth but I always end up need it. Also less pain.
For me, it was better having them when I did at 12/13 instead of later because I didn't like the look of them and would have hated them even more in my later teen years.
That way you have a nicer smile sooner. Also, as an adult you are judged more for your appearance so it can affect your job.
you will have better teeth when you get older