I don't think foul behaviour should be 'expected' of a teen. They do have more to contend with though as a direct result of real physiological changes in the brain. I still expect mine to treat other people well, although I understand they find this harder when they're feeling moody. Just like a peri menopausal/menopausal woman can't just be foul to everyone they meet for a few years 'it's my hormones, though, innit?'
There are certain functional brain changes in teens which have been seen with PET scanning. There is a lot of rewiring going on so that the brain becomes more mature. The prefrontal cortex is slowed down, so they have a tendency to risk taking behaviour and impulsiveness, a bit like when an adult is drunk.
They also have a genuine disturbance in their sleep cycles, staying up later and sleeping in longer. Hormonal influences on behaviour is very real, and can be seen in all animals. So teens do have a lot to contend with.
However, I do think that modern parenting plays a large part, in that many people overdo parenting in preteens, doing things for them which they are easily able to do themselves. They then fail to be responsible for their own things and behaviour, time management and so on, and are in effect underprepared for being a teen. If parents continue to try to control their teens lives as they get older the child rightly resents this and problems can start.
So the teen is caught being fairly clueless about being independent, but at the same time desperate to find their own feet. The parent finds it hard to trust their teen to look after themselves as they are used to picking up after them, nagging and organising them.
This combined with the hormonal and rewiring glitches can cause problems in behaviour. I do think how a parent responds has a huge effect on how the teen will behave.
We have always tried to give all our dcs as much independence, trust and responsibilities as possible for their ages. I think it gives them less to rebel against. So far we have two teens who are a pleasure to live with, but still two to go through this phase. So I expect people are hoping my younger two give me a run for my money 