People don't like to wait. I think that's a basic fact of life.
I don't think Bert Parks ever asked a future Miss America; "So, Miss Illinois, what are your hobbies?" and she replied "Well, Bert...I LIKE TO WAIT!" Anybody out there remember Bert Parks singing "There she is, Miss America..."
Back on topic. I think it's a combination of many things, including:
The ability to fast forward thru tv shows, microwaves heating your leftovers in minutes, computers giving us information instead of having to go to the library and looking things up, services now being delivered to our homes with the option of one day delivery. Etc, Etc,Etc. Progress has made us used to getting things conveniently and faster.
But, commercialization has also told us and our children how we NEED to buy their product because we "deserve" it. We "deserve" to be treated "special", to be spoiled.
Many people have become unaccustomed to having to wait, therefore they become impatient when it happens and more and more often get upset when they don't get that instant gratification.
It's also that many corporations have decided to understaff in order to make more profit.
It's also that according to the latest stats, the "average person" looks at their cell phones 74 a day. Some people actually have panic attacks if they have to do without their smart phones for a day.
I have heard working parents panic "OMG, how will my child get a hold of me when they are at school?" What do they think we did when there were no cell phones? It's not like we abandoned children to the wolves, if they needed to use the phone, they went to the school office.
And lastly, I don't think manners are being used as much as they used to. By young and old alike.