Why do toi think adults don't understand teenagers even though they were once teenagers themselves?

Because they shouts in front of friends.
Well well well
We will be adults one day.

Because they tend to stand up to the adults and do what they wrong. I am a teenager myself

Because maybe stuff happened in their life's!

i think because they know the wrong things they have done as teens and they dont want their kids to fo'llow in their foot steps, thats why. and they know they were immature when they were teens now, the are mature.