Too many parents are over concerned with having 'authority' over their offspring to admit to themselves that the job of a parent is to raise the next generation in such a way as to give them all the tools necessary so that they are able (a) to have a happy and successful life, according to what they themselves want (i.e. not necessarily what their parents or other people want for them) and (b) to resist those that would coerce them into something they wouldn't choose for themselves, given all the facts.
Being able to go from crying to get what they need (newborn baby) through childhood quarrels to negotiations (e.g. over salary and terms of employment) in a polite and firm manner, necessarily requires people to practice being on the opposite sides in arguments. Who safer to argue with than one's parents (provided, of course, that the parents aren't douches
)?
It means that a parent gradually hands over responsibility to their children in increments as they grow. By the time they are teenagers, they should be getting greater and greater freedom to be and express themselves. Certainly by the time they are 16 I see my job as no longer being their caretaker so much as being there as a back-up, a safety-net for when things go wrong (which they inevitably do).
If I cannot win an argument with a teenager, then I either don't know enough of the subject that I'm talking about (in which case I should ask for a time out and jolly well get myself educated on the subject) or I'm flat-out wrong, in which case I should concede to them in good grace. Neither position, in my experience, has
ever led to the teenager in question losing respect for me. Respect is earned, not imposed.