What happened to manners?

Today I attended my youngest daughter's graduation from high school. It was a morning commencement ceremony as the original date was postponed due to the threat of rain. Turns out I liked it as much as the the evening commencement my oldest daughter had in 2005.
Unfortunately the same thing happened this year as six years ago. I am referring to the families and friends of the graduates in the stands.
When did it become okay for audiences to talk through speeches, or the announcement of names in the graduating class?
When did it become okay to stand up and stretch blocking the view of those behind you?
When did it become okay to cheer and yell so loud and long, complete with airhorns, so that the other families cannot hear their graduates names being called?
I noticed this issue years ago at a talent show at a grade school. This continued through almost all school activities I attended.
Parents, who should know better, for whatever reason feel the need to talk to their neighbors during the entire show or meeting.
Is it any wonder teachers or instructors have a problem with kids sitting quietly in their seats, and listening to the lesson. They are not learning this important skill at home.
There is a time and a place for everything.
Talking through a movie, or a play, or a commencement ceremony is not acceptable behaviour.
Like the shoppers with an earpiece in their ear, talking to whoever is on the other end, totally clueless that the other shoppers around them don't really need to hear about the woes of the speakers private life that they feel obligated to share.
What concerns me the most is the fact that these offenders seem to be clueless...they will never change.
We seem to be living in a society that accepts this, and I am deeply saddened by the fact that there is a whole big group of folks out there who never learned that sometimes you just need to sit and listen. I learned this as a child, as my children did.
How did they miss this important part of growing up?