I've noticed a whole lot of people confuse schizophrenia with multiple personality disorder. Two completely different conditions. Why?

[c=#7700B2]they used to be considered as the same thing.. Also multiple personality disorder was once called split personality disorder and schizophrenia means split mind.. And Hollywood didn't help with the bad movies on mental illnesses [/c]

I was going to say Hollywood and remembered reading some definite treatise to the effect, but of course when I went looking for it, couldn't find it. Instead, there's this very technical explanation:
"Because it portrays images that are always seen as being external to the character, together with thoughts and ideas that in reality are internal, the cinema helps to further exacerbate the confusion. Thus, it becomes very difficult to distinguish a split personality from a hallucination because the visual nature of the cinema requires that both DID and schizophrenia must be shown as something external, tangible, and visible to the spectator. Resources such as using two parts played by different actors or conversations between two different personalities kindle doubt in the spectator as to whether what he or she is seeing really exists or is merely a visual representation of a mental process. This is a key point since it determines whether there are hallucinations or not." http://revistamedicinacine.usal.es/en/volumes/volume2/num4/998
Though, in real life, the two aren't always easy to tell apart either as discussed for example in https://www.ncbi.nlm.nih.gov/pubmed/18652789 "However, substantial data exist to document the elevated occurrence of psychotic symptoms in DID; awareness of these features is necessary to prevent diagnostic confusion."

I can only go on my own experiences, all the people I have known with MPD have been narcissist, and the multiple personalities they have created to manipulate or to get through a situation. Schizophrenia is not something you create to get yourself though anything, you have no control of it at all. But that's just my opinion

I think it is a common mistake.
Most mental illness is hard to understand and the criteria seems to be constantly changing so it gets confusing at times.

I was told that higher functioning autistic individuals are sometimes misdiagnosed with a mental illness.

unless they've had it or close to someone it can be confusing because there's more than just one type.

some folks thought i had it but.. apparently i have chimera syndrome... (i talk to the twin i absorbed while still in the womb. i'm two people.)

others like to talk to their thoughts... again not skitzoidism.

then.. like with many other disorders and diseases.. which is it? you have the diagnosed top tier then you go down the line of symptoms and issues... a pyramid or linear line of trickle down deciphering elements where one can possibly... that's possibly treat with therapy and meds.

... possibly.

They aren't related,but in popular culture you have the album QUADRAPHENIA,and the song,You're Never Alone with a Schizophrenic

when i was younger i used to think the same... dunno why but then after experiencing psychosis (which is the non chronic form of schizophrenia) obviously my attitude changed

I have epilepsy and people don't understand it. Ambulance is called, but never necessary; I have refused most of the time.

Why don't you tell us so we can know.

People generally don't know anything about mental illnesses

Because schizophrenia was falsely described as "split personality" in the old days,it is nothing of the sort it is a psychotic disorder,the personality of a person suffering from this condition is not split it is shattered by the nature of the disorder.