Adults vs the other (teens)

Forgive my naive nature and maybe even stupidity but: 

ok so since we are talking about teenagers (and as I happen to live with one), i see a clear need to express my opinion about the “Other” syndrome. 

so adults (and other machines) try to label adolescence and turn it into something more concrete and tangiable – “teenagers” – something that every other person would understand when you say “Oh, my daughter/son is going through the teenager period”.  Adults try to dominate this ’sensitive’ period of ‘becoming’.. (gotta love the tie-tying business that Dale Carnegie teaches teens..)

what I dont understand is the need for adults and their teenagers to alienate themselves from each other. why do teenagers think that their parents/guardians/teachers/etc are “too old to understand” and that it is somehow “different these days”? Likewise, why do adults want to control the youth but at the same time clearly label them as “the teenagers” – with obvious connotations in mind..?

this sense of “us vs them” is somewhat similar to Jacques Lacan’s ideas about culture divides and East/West dichotomies (ok i am blowing this up a bit, but you get my drift)..

the point is  -  why is adolescence such a pronounced period of life that is separated from all others (why isn’t there a divide between the elderly and the middle-aged?)..

so – is the ‘becoming’ of adolescence and its ‘affects’ the reason for this age war?