Medically, no, only a fragment of the population need them (a quarter? a third? sorry, I don’t have a dentist handy): just having irregular teeth is not medical reason enough for braces.
Societally, in the US more people need them than in other countries. The default value has become “perfect teeth;” dark or very irregular teeth are instinctively considered a sign of bad hygyene (in the sense of preventive medical care, not cleanliness). If you have dark teeth, people assume that you smoke like a chimney (I’ve had to explain the secondary effects of bystracycline on teeth to several coworkers); if you have irregular teeth, people assume that you either grew up in a trailer in the assend of Appalachia or never gave a hoot about your dental health.
Would you want your first impression in an interview to be “someone who doesn’t take care of his health at all”?
If you do need braces, it’s better to get them as a child; among other things, there are parts of an adult’s bones which are cartilage in a child; getting cartilage to take “the right shape” is easier than doing the same with bone.
PS: my horribly misaligned teeth have perfect bite. If I ever get to work in the US again, I’m asking my dentist for a certificate, it’s absurd how many times this has come up.