How bad do your teeth have to be to get braces?

Depends. Depends what you mean by "bad." you may think they look ok enough. The dentist also looks at how your teeth and jaws actually function - how much wear, whether teeth positions prevent good cleaning, even whether teeth positions and jaw size and shape are interfering with good breathing, swallowing and sleeping. There's a lot more to it than just crowding. Treatment now may prevent problems later.
Bad is "relative" Not bad at all. If you have some simple esthetic concerns with your teeth or smile, braces can improve upon them - - - and that would be of benefit to you. That is the key qualifier.
Braces. Some persons wanted a perfect smile with perfect alignment of teeth.Orthodontist ocasionally pull out some teeth that are crowded to make it fit.You can see the transformation after wearing braces.
Varies. If teeth don't look right, they don't function right either. If either you or your family dentist have even the slightest concern, go see a qualified orthodontic specialist for an opinion. May as well make your personal decision based on fact.