They don't, the reason you may not see servely autistic people in public is because they may live in special homes or at their parents house still. People with high functioning autism/aspergers can easily live by their own and can operate day to day like any other person. You may not even notice they have a disorder.
No, autistic people do not have a shorter lifespan. There is nothing about autism that would cause someone to have a shorter lifespan.
Autism Spectrum Disorder is a neurological condition, autistic people are born autistic - we do not know why people are autistic.
Autistic people (identity-first language) live as long as Neurotypical people, Autism doesn't impact on health in such a way that could shorten someone's life. In theory Autistic people have a slightly shorter lifespan because some Autistic people have problems identifying harmful behaviour - such as children who wander near water - also due to prejudice Autistic people may be more likely to be unemployed or be denied equal medical care which impacts on life.
Firstly, it's offensive for you to imply that autistic people are abnormal - autistic people are different to neurotypical people, not less than. A person is born autistic, it is not something that happens to 'normal' people or something that you turn into, you are always autistic.
No, not all Autistic children are savants. Many Savants are Autistic, but most Autistic people are as normal as Neurotypical people with no particularly special talents.
No, not all autistic people lack a sense of humour. There is a saying in the autism community: once you've met one autistic person...you've met one autistic person. autistic people are as different and varied as neurotypical people.
Employers do hire Autistic people, however normally when they do they don't realize that the person is Autistic. There is a lot of prejudice against Autistic people so even in areas where there are discrimination laws in place Autistic people often cannot find work, Autistic people normally have to hide their Autism from employers to avoid facing discrimination.
Your autistic child may not recognise their name as their name. Many autistic people are disconnected from how they are percieved by others, not all Autistic people accept the name given to them as representitive of them.
No, not all autistic people act the same - autistic people are as different and varied as neurotypical people. Like with neurotypical people all autistic people will share common traits, but once you meet one autistic person then you've met one autistic person...we're all very different.
Autistic people don't 'get' autism, Autistic people are born Autistic just like people are born African-American or born male/female. Tony Hawk thus was born Autistic, he became Autistic while he was still developing in his mothers womb.
No, autistic people are not 'crazy'. Many autistic people can have mental health issues but they're no more likely to have mental health issues than anyone else and often mental health issues in autistic people is more to do with how society treats autistic people - e.g. depression is more likely in autistic people who are bullied or face discrimination.
Depending on the species they can live in excess of 50 years. However many have shorter lifespans.